Muay Thai Weight Classes: Divisions and Weigh-Ins

There is no single answer to "what are the Muay Thai weight classes", and the reason is not that the sport is disorganised. It is that Muay Thai runs two parallel competitive systems that were built for different purposes, and each of them has its own ladder, its own units and — the part that actually matters to a fighter — its own moment at which you get put on the scale.

The professional side descends from the Thai stadium tradition and from Western boxing, and it counts in pounds. The amateur and Olympic-pathway side is governed by the International Federation of Muaythai Associations, and it counts in kilograms. A division called featherweight in one system does not exist in the other. And an athlete who plans a fight-week cut around the professional weigh-in and then enters an IFMA tournament has planned for a scale that will not be there.

This article quotes both rulebooks directly, notes two places where the published professional table contradicts itself, and sets out what each weigh-in structure does to the arithmetic of making weight. It is not a cutting protocol. It is the part of the problem you can actually look up.

Divisions in the WBC Muaythai professional ladder, from Minimum Weight at 100–105 lb to Heavyweight over 190 lb

WBC MuayThai Rules and Regulations, 2021, Rule 6.1

12 hours

Minimum rest the professional rulebook requires between the weigh-in and the contest, written in as a rehydration provision

WBC MuayThai Rules and Regulations, 2021, Rule 6.3.3

Amount over your qualified class at which an IFMA athlete is disqualified at the pre-contest weigh-in — a cap on the regain, not the cut

IFMA Rules and Regulations v3.057, 11 May 2026, Rule 11.1.2

Every morning

Frequency of the IFMA Competition Weigh-In during a championship, which removes the single-scale model entirely

IFMA Rules and Regulations v3.057, Rule 11.1

What this comes down to

Muay Thai has two division ladders, not one. The WBC Muaythai professional table runs 18 divisions in pounds; the IFMA elite table runs 14 for men and 11 for women, in kilograms, and the two do not map onto each other.
The professional weigh-in happens 24 to 36 hours before the scheduled fight time, and the same rulebook separately requires a minimum of twelve hours' rest after it "in order to safely rehydrate". A rehydration window written into a rulebook is rare, and it is the single most useful line in the document.
IFMA weighs athletes every morning of competition, and adds a pre-contest check at which being 5% above the qualified class is a disqualification. That is a rule aimed at the rebound rather than the descent.
Under IFMA rules, competition starts no earlier than three hours after the Competition Weigh-In closes. Three hours is not a rehydration window in any meaningful sense, which is the point.
The published WBC Muaythai table contains at least two internal conversion inconsistencies between its pound and kilogram columns. If you are weighing to a kilogram scale against a pound-defined limit, verify the limit with the sanctioning body rather than the table.
The professional five-pound provision is a negotiated tolerance for a bout that is already made, not a weight allowance you can plan around. It requires that all parties agree.
Everything about a Muay Thai cut is downstream of which of these two systems you are competing in. Choose the division after you know the format, never before.

Two sports wearing the same name

Start with the thing that causes most of the confusion. When a Thai stadium, a Western promotion or a sanctioning body such as the WBC Muaythai puts on a professional card, the divisions are the boxing divisions: minimum weight, light flyweight, flyweight, and upward in pounds, with the familiar super- and light- prefixes filling the gaps. That ladder exists because professional Muay Thai grew up alongside professional boxing in Thailand and inherited its commercial architecture, including its weight table.

When IFMA runs a World Championship, a World Games event or any part of the Olympic pathway, the divisions are metric and they are spaced differently. The gaps are wider at the bottom and narrower relative to body mass at the top, because the table was designed for tournament brackets rather than for single-bout matchmaking.

Neither ladder is more official than the other. They serve different competitions. But a fighter who trains in a gym where both amateurs and professionals prepare will hear both sets of names used interchangeably, and that is where planning errors start.

The practical test is simple: ask who is sanctioning the bout and which document they are working from. If the answer is a professional sanctioning body, you are on the pound ladder with a day-before scale. If the answer is a national federation running an IFMA-sanctioned tournament, you are on the kilogram ladder with a scale every morning.

The professional ladder, as published

The WBC Muaythai Rules and Regulations set the divisions out in Rule 6.1. There are eighteen, and the table gives each limit in pounds with a kilogram conversion beside it.

Division	Limit
Minimum Weight	from 100 lb (45.454 kg), not over 105 lb (47.627 kg)
Light Flyweight	over 105 lb, not over 108 lb (48.987 kg)
Flyweight	over 108 lb, not over 112 lb (50.802 kg)
Super Flyweight	over 112 lb, not over 115 lb (52.163 kg)
Bantamweight	over 115 lb, not over 118 lb (53.524 kg)
Super Bantamweight	over 118 lb, not over 122 lb (55.338 kg)
Featherweight	over 122 lb, not over 126 lb (57.153 kg)
Super Featherweight	over 126 lb, not over 130 lb (58.967 kg)
Lightweight	over 130 lb, not over 135 lb (61.235 kg)
Super Lightweight	over 135 lb, not over 140 lb (63.503 kg)
Welterweight	over 140 lb, not over 147 lb (66.678 kg)
Super Welterweight	over 147 lb, not over 154 lb (69.853 kg)
Middleweight	over 154 lb, not over 160 lb (72.575 kg)
Super Middleweight	over 160 lb, not over 168 lb (76.204 kg)
Light Heavyweight	over 168 lb, not over 175 lb (79.379 kg)
Cruiserweight	over 175 lb, not over 190 lb (86.167 kg)
Heavyweight	over 190 lb (86.168 kg)

Two features are worth noticing before the numbers. First, the ladder is dense at the bottom — three pounds separates several of the lower divisions — and sparse at the top, where cruiserweight covers a fifteen-pound band and heavyweight is unbounded. That asymmetry is inherited from boxing and it means the cost of missing a division is not constant across the ladder. At super flyweight, three pounds is a division. At cruiserweight it is a rounding error.

Second, the floor is a hard one. Rule 6.3.1 states that a boxer must weigh at least 100 pounds to qualify for minimum weight. There is no professional division below it.

The kilogram column does not agree with itself

This is the kind of detail that sounds pedantic until it costs someone a fight, so it is worth being explicit about.

The published table gives Super Bantamweight as "over 118 pounds (53.524 kg), but not over 122 pounds (55.338 kg)", and gives Featherweight, on the next line, as "over 122 pounds (55.225 kg), but not over 126 pounds (57.153 kg)". The same 122-pound boundary is converted twice, to two different kilogram values, 113 grams apart. Only one of them can be right; 122 lb is 55.338 kg.

Separately, Light Flyweight is printed as "Must be over 105 pounds (47. kg.)" — a truncated conversion where 105 lb is 47.627 kg, the value the table gives correctly one line above.

Neither error changes what a fighter has to do, because the pound value is the governing one in a pound-defined system. But it does change what a fighter should trust. If your scale reads kilograms and your division is defined in pounds, convert the pound limit yourself and confirm the figure with whoever is sanctioning the bout. Do not weigh to a printed conversion, in this rulebook or any other.

This is a general habit worth having. A weight limit is a legal boundary, and the arithmetic that gets you to it is your responsibility, not the promoter's. The same discipline applies to the divisions in MMA, where the ABC table is defined in pounds and every non-American commission works in kilograms.

The professional weigh-in, and the twelve-hour rule

Rule 6.2.1 sets the timing:

The boxers must weigh-in without clothes (underpants permitted) one-day before the contest in a time period of 24-36 hours before the scheduled fight time.

That is a wider window than most fighters assume, and the width matters. Twenty-four hours and thirty-six hours are meaningfully different recovery periods, and the rulebook permits either. A fighter planning a fight week around "the day before" without knowing which end of that window applies has left a third of their recovery time unspecified.

Rule 6.2.2 then allows the supervisor to make exceptions in certain circumstances, which is the standard escape hatch and a reminder that the sanctioning body, not the rulebook, is the final authority on your particular bout.

Then comes the provision that makes this rulebook unusual. Rule 6.3.3:

The boxer must have a minimum time of twelve hours to rest after the weigh-in to in order to safely rehydrate and be in good physical condition for the contest.

Read that carefully, typo and all. It is a rulebook stating a minimum rehydration period as a condition of competition. Most combat-sport rulebooks specify when the weigh-in happens and say nothing at all about what has to happen afterwards; the recovery window is left as a consequence of the schedule rather than a requirement of it. Here it is a requirement, and it is written in health language: safely rehydrate, good physical condition.

The practical consequence is that in WBC Muaythai competition the rehydration window is not merely likely to be long enough to matter. It is required to be. That does not make an aggressive acute cut sensible, and the rule does not say it does. But it does mean this format sits at the opposite end of the spectrum from the grappling formats where an athlete weighs in and competes minutes later.

Missing weight: the five-pound provision

Rule 6.3.2:

The matched boxers for championships must be contested within no more than five (5) pounds weight difference if a boxer if overweight and the contest is agreed by all parties to continue.

Three things travel with that number and all three get dropped when it is repeated in gyms.

It applies to a boxer who is already overweight — it is a salvage mechanism for a bout that has been made and a fighter who has missed, not an allowance to plan against. It requires that all parties agree, which means the opponent can decline and the fight does not happen. And it caps the difference between the two athletes, which is not the same as five pounds over the limit; if the opponent has made weight comfortably under, the arithmetic is different from the case where they are exactly on it.

For heavyweight, Rule 6.3.4 provides for an agreed catchweight, in complete written agreement between both camps and the sanctioning body before sanctioning takes place. That is the correct way to fight at a weight that is not a division: agree it in advance, in writing, and make it the official weight. Not by missing and negotiating on the night.

The amateur ladder: IFMA's kilogram table

The IFMA Rules and Regulations, revised 11 May 2026, set the weight classifications in Rule 4. For the Masters and Elite pathway the men's divisions run:

45 kg (marked for inclusion into selected multi-sport events only, subject to Executive Committee approval), 48, 51, 54, 57, 60, 63.5, 67, 71, 75, 81, 86, 91 and +91 kg, the last of which Masters 40+ and Masters 45+ athletes are not permitted to contest.

The women's Masters and Elite divisions run 45, 48, 51, 54, 57, 60, 63.5, 67, 71, 75 and +75 kg.

Note the shape. Three-kilogram steps from 45 to 60, then 3.5 to 63.5, then a widening — 67, 71, 75 — and then six-kilogram steps at the top. A 3 kg step at 48 kg is 6.25% of body mass; a 5 kg step at 86 kg is 5.8%. The ladder is more even in proportional terms than the professional one, which is what you would expect from a table designed for tournaments where every athlete in a bracket fights several times in a weekend.

The under-24 tables mirror the elite ones. The under-18 women's table adds a 42 kg division below 45. The junior tables descend a long way further, to 16 kg in the under-8 category, and this is worth saying plainly: those divisions exist to bracket children by size, not to give them a target to cut to. Nothing in the weight-cutting literature applies to them.

Three weigh-ins, and the one that changes everything

The structural difference between the two systems is not the ladder. It is Rule 11.1, which specifies three separate weight checks:

Official Weigh-In: 1 day prior to the start of competition; Competition Weigh-In: Each morning of competition; and Pre-Contest Weigh-In: Any time prior to the Athletes contest.

The Official Weigh-In happens only at the Technical Delegate's discretion. The Competition Weigh-In happens every morning that an athlete is scheduled to fight, and Rule 11.2 requires a medical examination by the appointed doctor immediately before it. Rule 11.3.3 allows one presentation on the scale per day: "The weight recorded on that presentation is final."

Then Rule 11.1.2, which is the sentence that reorganises everything:

If the Athletes pre-contest weight is found 5% above their qualified weight classification, or equal to the next weight classification they will be disqualified.

That is a ceiling on how heavy you may be at the moment you fight. Not on how light you were at the scale. IFMA is regulating the rebound.

An athlete at 71 kg who has cut hard to make the division and rehydrated back to 76 kg is over the 74.55 kg threshold and is disqualified — after making weight. The rule converts a large acute cut from a competitive advantage into a competitive liability, because the size you gain back is the thing that ends your tournament.

And Rule 11.1 sets the floor on the other side: "Competition shall start no earlier than three (3) hours after the close of the Competition Weigh-in." Three hours, every morning, with a 5% ceiling waiting at the ring. There is no version of a fight-week water cut that survives that structure.

A worked scenario, and why the two formats are not comparable

Take a hypothetical 75 kg athlete deciding between a professional bout at Super Welterweight (154 lb, 69.853 kg) and an IFMA tournament at 71 kg. The absolute descent looks similar — roughly 5.1 kg to the professional limit, 4 kg to the amateur one. It is the same fighter and nearly the same number.

The formats make them entirely different problems.

In the professional bout, the athlete steps off the scale somewhere between 24 and 36 hours before the fight, with at least twelve hours of rest required by rule, and the whole recovery literature applies: fluid, sodium and carbohydrate together, with the regain measured in the published cohorts at meaningful multiples of a kilogram. That is the format the fight-week research was mostly conducted in, and the figures in how much weight you can cut before a fight describe it.

In the IFMA tournament, the athlete weighs 71 kg or less every morning, competes three hours later, and must be under 74.55 kg at the ring on each of those days. There is no window to recover into and no single scale to peak for. The 4 kg has to be gone before the tournament starts and it has to stay gone for its duration. That is not an acute cut with a different number attached; it is a different job entirely — a longitudinal descent that lands on the division and holds there.

This is the same structural point that makes grappling weigh-ins their own category. When there is no recovery window, the acute phase has nothing to be acute for.

Thailand, and what we could and could not confirm

The Thai stadium system is the origin of professional Muay Thai and the hardest part of this article to source properly, which is worth saying directly rather than papering over.

What is well established and checkable is the sanctioning framework at the international professional level: the WBC Muaythai rulebook quoted above, which is published openly and dated. What is repeated frequently in English-language coverage but which we could not confirm against a primary Thai regulatory document during research for this article includes the specific minimum ages applied under the Sports Authority of Thailand's Boxing Board of Control, the stadium-specific matchmaking conventions at Lumpinee and Rajadamnern, and the exact weight-difference conventions those stadiums apply to non-title bouts.

Those things may well be exactly as commonly described. We are not saying they are wrong. We are saying we did not reach a primary document that states them, and this site does not print a rule as current on the strength of a secondary summary. If you are fighting in Thailand, the promoter and the stadium hold the operative version, and a boxer's book carries the record that governs your matchmaking.

What the nutrition literature adds, and where it stops

The 2025 International Society of Sports Nutrition position stand on combat-sport weight management is the most useful published document on the descent itself, and it is worth reading alongside whichever rulebook governs your bout rather than instead of it.

Two of its figures bear directly on Muay Thai. The stand puts habitual off-camp weight at 12–15% above the division requirement, which for a 71 kg IFMA athlete is roughly 79.5 to 81.7 kg and for a Super Welterweight is roughly 78.2 to 80.3 kg. And it describes acute water-loss strategies during fight week — sauna, hot water immersion, wraps — at optimally around 2–4% of body mass within 24 hours of weigh-in, explicitly and inside the same sentence, with appropriate supervision.

Where that stops applying to Muay Thai is a matter of format rather than sport. The acute-phase figure was described for competitions with a recovery window on the other side of the scale. Under IFMA rules there is no such window, and the 5% pre-contest ceiling penalises the regain that the figure assumes. Borrowing the number across is the exact error the position stand's own framing warns against.

There is also no published figure for what is suitable to attempt without supervision, in any format. That absence is not an oversight to be filled in by a coach's judgement.

What breaks first, in this sport specifically

The failure sequence in Muay Thai has a shape that differs from single-bout sports, and it is worth naming.

The tournament format punishes the plan, not the day. A fighter who arrives at an IFMA championship having made weight by the narrowest possible margin has to do it again tomorrow, and the day after, on progressively less recovery. The athlete who was two kilograms clear on day one is in a different competition by the semi-final.

The daily medical check is a real gate. Rule 11.2 puts a doctor immediately before the scale every morning. That is not a formality; a fighter who is visibly compromised does not get to the scale to find out whether they made it.

In the professional format, the thirty-six-hour end of the window is a trap in reverse. A camp that plans for 36 hours of recovery and gets 24 has lost a third of it. Ask the promoter which it is, in writing, before the descent is planned around it.

And in both formats, the low divisions have no margin. Three pounds at super flyweight, or three kilograms at 48 kg, is a division. The proportional cost of a small absolute error rises the further down the ladder you go, and the ladder goes a long way down in this sport.

Choosing a division when there are two ladders

The useful order of operations is the reverse of what most fighters do.

Establish the sanctioning body first, because that determines the ladder and the weigh-in structure. Establish the weigh-in structure second, because that determines whether an acute phase is coherent at all. Only then look at the divisions and pick one — and pick it against your actual habitual weight rather than the weight you can reach once.

For a fighter competing in both systems in the same year, that will sometimes mean competing at what looks like two different weights. That is not an inconsistency. It is the correct response to two formats that ask different questions. A plan built backwards from a known weigh-in date and a known format is the only kind that survives contact with either, which is the logic fight camp planning is built on.

What we could not verify

Stadium-level rules in Thailand. We could not reach a primary Thai regulatory document for Lumpinee or Rajadamnern matchmaking conventions, minimum ages, or their specific weight-difference allowances. The figures circulating in English-language sources may be accurate; we did not confirm them and do not print them as rules.
The current WBC Muaythai rulebook version. The document we quote is the published 2021 Rules and Regulations, retrieved from the sanctioning body's own site. Rulebooks are amended; confirm the operative version with the sanctioning body for your bout.
The kilogram conversions in that table. We identified two internal inconsistencies. We have not audited every row, and the presence of two errors means the column as a whole should be treated as informational rather than governing.
IFMA junior and Masters tables in full. We transcribed the Masters and Elite men's and women's ladders and spot-checked the U24 and U18 tables. The complete age-group tables run to under-8 and are best read from the rulebook itself.
Nothing here is specific to you. Not your division, your body composition, your medical history or the particular commission or federation sanctioning your next bout.

Questions fighters ask

What are the Muay Thai weight classes?

There are two sets. Professionally, the WBC Muaythai rulebook lists eighteen divisions in pounds, running from Minimum Weight (100–105 lb) through Light Flyweight, Flyweight, Super Flyweight, Bantamweight, Super Bantamweight, Featherweight, Super Featherweight, Lightweight, Super Lightweight, Welterweight, Super Welterweight, Middleweight, Super Middleweight, Light Heavyweight and Cruiserweight to Heavyweight (over 190 lb). In amateur and Olympic-pathway competition, IFMA uses a metric ladder: for elite men, 48, 51, 54, 57, 60, 63.5, 67, 71, 75, 81, 86, 91 and +91 kg, with a 45 kg division for selected multi-sport events; for elite women, 45 through 75 kg and +75 kg. The two systems do not correspond, so the first question about any bout is which of them is sanctioning it.

When do Muay Thai fighters weigh in?

It depends entirely on the system. Under WBC Muaythai professional rules the weigh-in happens one day before the contest, within a window of 24 to 36 hours before the scheduled fight time, and the same rulebook requires a minimum of twelve hours' rest afterwards to rehydrate. Under IFMA rules there is a Competition Weigh-In every morning of competition, with the bout starting no earlier than three hours after that weigh-in closes, plus an optional Official Weigh-In the day before the championship and a Pre-Contest Weigh-In at any point before the contest. A professional weigh-in gives you a day. An IFMA weigh-in gives you three hours, repeatedly.

What is the IFMA 5% rule?

IFMA Rule 11.1.2 states that if an athlete's pre-contest weight is found to be 5% above their qualified weight classification, or equal to the next weight classification, they will be disqualified. It is a limit on how heavy you may be when you actually fight, rather than on how light you were at the scale. For a 71 kg athlete the threshold is 74.55 kg. The effect is to remove the incentive to cut aggressively: any mass you put back beyond 5% of your division ends your tournament, so the advantage a large acute cut is supposed to buy cannot be realised.

Can you cut weight for a Muay Thai fight?

In professional competition, where the weigh-in is 24 to 36 hours out and twelve hours' rest is required by rule, the fight-week literature broadly applies — including the 2025 ISSN position stand's description of acute water loss at optimally around 2–4% of body mass within 24 hours of weigh-in, which that document conditions on appropriate supervision in the same sentence as the figure. In IFMA competition the structure makes it incoherent: you weigh in every morning, fight three hours later, and are disqualified if you are 5% over your class at the ring. There is nothing to recover into and a penalty for recovering. The correct plan there is a longitudinal descent that arrives at the division and holds.

How much can a Muay Thai fighter be over the limit?

In WBC Muaythai championship competition, Rule 6.3.2 permits a contest to go ahead with no more than five pounds of weight difference between the boxers where one is overweight and all parties agree to continue. Three qualifications travel with that. It applies to a fighter who has already missed, not as an allowance to plan for; it caps the difference between the two athletes rather than the excess over the limit; and the opponent can refuse, in which case there is no bout. For heavyweight, Rule 6.3.4 allows an agreed catchweight settled in writing between both camps and the sanctioning body before sanctioning.

What is the lightest Muay Thai weight class?

In the professional WBC Muaythai table it is Minimum Weight, which runs from 100 pounds up to and including 105 pounds, and Rule 6.3.1 states that a boxer must weigh at least 100 pounds to qualify for it. There is no professional division below that floor. On the IFMA side the elite ladder starts at 45 kg — marked in the rulebook for inclusion into selected multi-sport events only, subject to Executive Committee approval — with 48 kg the lowest routinely contested elite division. The junior tables descend much further, but those exist to bracket children by size and carry no cutting implication whatsoever.

Are Muay Thai and kickboxing weight classes the same?

No, and they are not the same as boxing's either, despite the shared division names on the professional side. Professional Muay Thai under the WBC Muaythai rulebook inherits the boxing ladder in pounds. Amateur Muay Thai under IFMA uses a metric ladder built for tournament brackets. Kickboxing organisations maintain their own tables, which differ again between promotions and between amateur federations. The division name is not portable information; the governing rulebook is. Always check the limit against the document of the body sanctioning your specific bout rather than against a name you recognise.

Does the gi or kit count at a Muay Thai weigh-in?

Under WBC Muaythai Rule 6.2.1 professional boxers weigh in without clothes, with underpants permitted. Under IFMA Rule 11.3.2 athletes weigh in "in suitable lightweight undergarments, and in a fully prepared state for competition", which the rulebook illustrates with no socks, facial hair shaved and toenails trimmed. Neither system weighs a fighter in fight kit. This differs from some grappling rule sets, where the uniform is weighed with the athlete, so it is not a detail to assume across sports.

What happens if I miss weight at an IFMA event?

Rule 11.3.1 states that an athlete may only compete in the weight classification for which they qualified at the weigh-in, and that an athlete who does not attend their weigh-in is automatically disqualified. Failing to make the class at the Competition Weigh-In means disqualification from that competition. There is one narrow exception: Rule 11.3.4 allows a 0.5 kg allowance for an under-24 athlete, approved by the Technical Delegate, who is likely to fail because of contentious travel circumstances — and that athlete must then make the Pre-Contest Weigh-In without exception on their first day of competition.

How many times can I get on the scale?

Once per presentation, in both systems, and the recorded weight is final. IFMA Rule 11.3.3 states that a competitor may present at the official scales only once at the weigh-in each day and the weight recorded on that presentation is final. This matters more than it sounds: there is no "let me try again in twenty minutes" built into the rules, so the margin has to exist before you arrive at the venue, not be found in the corridor outside it. Check-scale practice varies by event; the official scale does not.

Why does the professional weigh-in window vary between 24 and 36 hours?

Because the rulebook sets it as a range rather than a fixed point: Rule 6.2.1 requires the weigh-in one day before the contest, within 24 to 36 hours of the scheduled fight time, and Rule 6.2.2 permits exceptions agreed with the supervisor. The practical consequence is that a third of your recovery time is unspecified until someone tells you the schedule. A camp that plans for 36 hours and receives 24 has lost twelve hours of rehydration it had already allocated. Ask the promoter for the confirmed time before planning the descent around it, not after.

Is the twelve-hour rehydration rule common in combat sports?

No, and that is what makes it worth knowing. WBC Muaythai Rule 6.3.3 requires a minimum of twelve hours' rest after the weigh-in "in order to safely rehydrate and be in good physical condition for the contest". Most combat-sport rulebooks specify when the scale happens and leave the recovery period as an accident of the schedule. Writing a minimum recovery period into the rules treats rehydration as a condition of competing rather than as the athlete's private problem. It does not make a large acute cut advisable, and the rule makes no such claim.

Do the same weight-cut percentages apply to amateur and youth Muay Thai?

No. The published combat-sport weight literature, including the 2025 ISSN position stand, is dominated by adult professionals and mostly male cohorts, and its figures were described for formats with a recovery window between weigh-in and competition. IFMA's junior tables run down to 16 kg in the under-8 category; those divisions exist to bracket children by size. Applying adult acute-loss percentages to a growing athlete is an extrapolation with nothing underneath it, and the daily-weigh-in structure of amateur competition removes the recovery window that the percentages assume in any case.

Where do I find the current rules for my fight?

From the body sanctioning it, in writing, before you plan the cut. For IFMA competition that is the IFMA Rules and Regulations in their current revision, held by your national federation, plus the event outlines issued by the organising committee. For a professional bout it is the sanctioning body's own rulebook and the promoter's confirmed schedule. Rulebooks are amended and event outlines override general expectations. Anything you read about your division on a website — including this one — is a starting point for that question, not an answer to it.

Sources

Sourced to

WBC MuayThai Rules and Regulations — World Boxing Council MuayThai, 2021; Rule 6 (weight divisions and weigh-in), Rules 6.2.1, 6.3.1–6.3.4
IFMA Rules and Regulations v3.057 — International Federation of Muaythai Associations, revised 11 May 2026; Rule 4 (weight classifications), Rule 11 (medical examination and weigh-ins)
IFMA Rules and Regulations v2.04 — International Federation of Muaythai Associations, 2023 revision, retained for comparison of earlier weigh-in provisions
International society of sports nutrition position stand: nutrition and weight cut strategies for mixed martial arts and other combat sports — Ricci AA et al., Journal of the International Society of Sports Nutrition, 2025;22(1):2467909. DOI 10.1080/15502783.2025.2467909, PMID 40059405
An alternative structured weight management protocol to rapid weight loss in mixed martial arts: a prospective interventional study — Maurício CA et al., Frontiers in Nutrition, 8 October 2025;12:1581698. DOI 10.3389/fnut.2025.1581698, PMID 41132567
Acute-Weight-Loss Strategies for Combat Sports and Applications to Olympic Success — Reale R, Slater G, Burke LM, International Journal of Sports Physiology and Performance, 2017;12(2):142–151. DOI 10.1123/ijspp.2016-0211
Muaythai at the 2025 World Games — competition weight categories — International World Games Association event record, 2025, used only to cross-check which IFMA divisions were contested
A Coach and Manager's Guide — International Federation of Muaythai Associations, competition guidance for team officials
Unified Rules of Mixed Martial Arts — Association of Boxing Commissions and Combative Sports, revision 8.2026, cited for contrast with the professional MMA division table
Muscle contraction velocity, strength and power output changes following different degrees of hypohydration in competitive olympic combat sports — Pallarés JG et al., Journal of the International Society of Sports Nutrition, 2016;13:10. DOI 10.1186/s12970-016-0121-3, PMID 26957952

Plan the descent, don't guess it

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Muay Thai weight classes and weigh-ins