Complete reference for Muay Thai weight classes — Lumpinee Stadium, ONE Championship, and WBC Muaythai standards, with notes on weight cutting and how to choose your class.
Your weight class is whichever class you can comfortably make on weigh-in day without dangerous cutting. For a first fight, that means within 4-6 pounds of your walking weight (the weight you sit at when you're training normally and not cutting). If you weigh 142 lb walking, fight at 147 (welterweight) rather than trying to drop to 140 (junior welterweight).
The temptation to drop a class for a perceived size advantage almost always backfires for first-time competitors. The fitness penalty from a hard cut is bigger than the size advantage you get on fight night. Save aggressive weight management for when you have several fights of experience and a proper sports nutritionist running your cut.
The traditional Thai stadium weight classes match the WBC Muaythai professional divisions and roughly mirror Western boxing weight class structures.
| Class | Limit (lb) | Limit (kg) |
|---|---|---|
| Mini Flyweight | 105 | 47.6 |
| Junior Flyweight | 108 | 49 |
| Flyweight | 112 | 50.8 |
| Junior Bantamweight | 115 | 52.2 |
| Bantamweight | 118 | 53.5 |
| Junior Featherweight | 122 | 55.3 |
| Featherweight | 126 | 57.2 |
| Junior Lightweight | 130 | 58.9 |
| Lightweight | 135 | 61.2 |
| Junior Welterweight | 140 | 63.5 |
| Welterweight | 147 | 66.7 |
| Junior Middleweight | 154 | 69.8 |
| Middleweight | 160 | 72.6 |
| Super Middleweight | 168 | 76.2 |
| Light Heavyweight | 175 | 79.4 |
| Cruiserweight | 190 | 86.2 |
| Heavyweight | 209 | 95 |
| Super Heavyweight | 209 | 95 |
The most competitive Lumpinee weight classes historically are between Junior Featherweight and Lightweight (122-135 lb). The depth of Thai talent in those divisions is unmatched anywhere in the world.
ONE Championship uses different weight classes than traditional Thai stadiums and requires a hydration test (athletes must rehydrate to within 102% of their fight weight before the bout) which fundamentally changes how cuts work. ONE's divisions are spaced wider apart than Lumpinee's.
| Class | Limit (lb) | Limit (kg) |
|---|---|---|
| Atomweight | 115 | 52.2 |
| Strawweight | 125 | 56.7 |
| Flyweight | 135 | 61.2 |
| Bantamweight | 145 | 65.8 |
| Featherweight | 155 | 70.3 |
| Lightweight | 170 | 77.1 |
| Welterweight | 185 | 83.9 |
| Middleweight | 205 | 93 |
Cutting weight for Muay Thai follows similar principles to other combat sports. For a first fight, don't cut more than 4-6 pounds. For ranked or championship bouts, work with a sports nutritionist and follow a structured plan over the 8-12 weeks leading into the fight rather than trying to crash-cut in the final week.
ONE Championship's hydration test rule has changed how many fighters approach weight management — you can't crash-cut and rehydrate twenty pounds anymore. This rule has reduced injuries and produced healthier fighters at fight time, even though it requires more disciplined daily nutrition during camp.
Weigh-ins typically happen the day before the fight (24-hour weigh-ins) at most modern Muay Thai promotions, allowing fighters time to rehydrate before competing. Some traditional Thai stadium fights have day-of weigh-ins, which means fighters cannot cut as aggressively.
At weigh-in, you strip down (varies by promotion — some allow underwear, some require nude), step on the scale, and the official records your weight. If you miss weight, the consequences range from a percentage of your purse going to your opponent (most common) to the fight being canceled. ONE Championship additionally requires a hydration test within 1-3 days of weigh-in. Once weighed in successfully, you eat, drink, and recover until fight time.