What this calculator does
Find out which boxing or MMA weight class a weight puts you in, and how close you are to the limit. Fights are split into weight classes, also called divisions, so fighters meet opponents of a similar size. Each class has a top weight, called its limit. A fighter belongs to the lightest class whose limit they make at the weigh-in. Boxing has seventeen divisions from 105 lb up to heavyweight. MMA (mixed martial arts) has fewer, wider ones, so the same weight can land in quite different places.
Enter a weight in pounds or kilograms and pick the list. The calculator names the division and gives its range and limit in both units. It says how far under the limit the weight is, and how much would need to come off to make the next division down. It also shows the full table of limits, with the other names the governing groups use.
Where it's used
Why this math matters outside the classroom:
- Fight-week planning. A fighter at 152 lb sees they are 2 lb under the 154 lb super welterweight limit and 5 lb over welterweight.
- Metric weigh-ins. Gyms abroad weigh fighters in kilograms, so 66.6 kg is converted to 146.8 lb to confirm it makes the 147 lb welterweight limit.
- Comparing sports. Fans check that a 155 lb MMA lightweight would be a boxing middleweight, 1 lb over the 154 lb super welterweight limit.
- Unit conversion practice. Students convert a 160 lb limit to kilograms by multiplying by 0.45359237, which gives about 72.57 kg.
- Matchmaking. Local promoters check whether two fighters, at 133 lb and 136 lb, fall in the same MMA division before booking them.
Grade level and standards: Grade 6; Common Core State Standards for Mathematics 6.RP.A.3.d. © Copyright 2010. National Governors Association Center for Best Practices and Council of Chief State School Officers. All rights reserved.
How to use it
- Enter the weight and choose lb or kg.
- Pick the list: boxing as used by the WBA, IBF and WBO; boxing with the WBC's extra bridgerweight class; MMA's traditional divisions; or every class in the Unified Rules of MMA.
- Read the division, its limit, and how far under it the weight is.
- Open the table to compare every division's limit in pounds and kilograms.
What the inputs mean
- Weigh-in weight
- The weight at the official weigh-in, usually the day before the fight. Kilograms are converted using 1 lb = 0.45359237 kg exactly.
- Sport and division list
- Boxing has four major sanctioning bodies, the groups that run title belts. They share the same limits but name some classes differently. The WBA and WBC say 'super' (super lightweight) where the IBF and WBO say 'junior' (junior welterweight). The WBC also has bridgerweight, up to 224 lb. In 2017 the Unified Rules of MMA added four in-between classes that many promotions (the companies that put on fights) don't use.
Formula and method
division = the lightest class with limit ≥ weight class range: over the previous limit, up to and including its own limit pounds = kilograms ÷ 0.45359237 room under the limit = limit − weight to make the class below = weight − lower class limit
The ≥ sign means "at or above". A weight class is a range. In boxing, for example, welterweight covers everything over 140 lb up to and including 147 lb. A fighter who weighs exactly the limit makes the weight. A fighter even a fraction of a pound over does not.
Limits are set in pounds, so a weight in kilograms is converted first. The table also shows each limit in kilograms, rounded to two decimals. For example, 147 lb is 66.68 kg.
The heaviest class has no upper limit. In boxing, heavyweight starts above cruiserweight's 200 lb, or above 224 lb where bridgerweight is recognized. In MMA, the Unified Rules cap heavyweight at 265 lb, with super heavyweight above it.
Worked example
An invented boxer weighs in at 152 lb and wants to know where that sits on the WBA, IBF and WBO list.
- 152 lb is over the 147 lb welterweight limit but not over 154 lb, so it's super welterweight (the IBF and WBO call it junior middleweight).
- Room under the limit: 154 − 152 = 2 lb.
- To make welterweight instead, the boxer would need to lose 152 − 147 = 5 lb.
- The next class up is middleweight, limit 160 lb. The 154 lb limit is 154 × 0.45359237 = 69.85 kg.
Result: At 152 lb a fighter fits super welterweight, 2 lb under its 154 lb limit.
Understanding the result
The division shows where the weight fits today, not always where a fighter competes. Most fighters weigh more day to day than they do at the weigh-in, and cut weight before it. So a fighter's everyday weight is often one division or more above the class they fight in.
Being right at a limit leaves no room for error. Commissions handle a missed weight in different ways. Often it's a fine, a catchweight fight (at a weight both sides agree on) or losing the chance to win a title.
Assumptions and limitations
- Limits are the professional ones published for the sport as a whole. A promotion or a women's division may use only some of the classes.
- The limits are applied as at a title-fight weigh-in. In MMA, the Unified Rules recommend keeping the custom of a one-pound allowance for non-title fights, but only where the fight contract or local rules provide for it.
- Bridgerweight appears only on the WBC list.
- Amateur and Olympic boxing, kickboxing and grappling use different classes.
- Catchweight fights are agreed one at a time and aren't on any list.
- Sanctioning bodies and commissions can change their divisions. Their official rules come first over this table.
Frequently asked questions
Why do boxing and MMA use different limits?
They grew up separately. Boxing has added in-between classes over a century, so its lighter divisions are only 3 or 4 lb apart. MMA started with gaps of 10 lb or more. A 155 lb MMA lightweight would be a boxing middleweight, just over the 154 lb super welterweight limit.
What is bridgerweight?
It's a boxing class the WBC introduced in 2020. It's for fighters over the 200 lb cruiserweight limit and up to 224 lb, who would otherwise face much bigger heavyweights. The other major bodies go straight from cruiserweight to heavyweight.
What are the 2017 MMA weight classes?
In 2017 the Association of Boxing Commissions added four classes to the Unified Rules. They are super lightweight (165 lb), super welterweight (175 lb), super middleweight (195 lb) and cruiserweight (225 lb). The aim was smaller jumps between divisions. Promotions choose whether to use them.
Is 'junior' the same as 'super' in boxing?
Yes. Super lightweight and junior welterweight are the same 140 lb class; the name depends on the sanctioning body. In the same way, 105 lb is called minimumweight, strawweight or mini flyweight.
Sources
- Association of Boxing Commissions: Unified Rules of Mixed Martial Arts (weight classes and one-pound allowance) (checked 2026-10-19)
- IMMAF: ABC unanimously approves additional weight classes for MMA (July 2017) (checked 2026-10-19)
- World Boxing Council: A new weight division, bridgerweight (checked 2026-10-19)
How this calculator is checked
Method: Division limits from the Unified Rules of Mixed Martial Arts (with the ABC's 2017 additions and strawweight) and the professional boxing limits shared by the WBA, WBC, IBF and WBO, including the WBC's bridgerweight; exact pound–kilogram factor. The calculation is covered by automated tests with known reference values and edge cases. Last updated 2026-10-18. Found a problem? Tell us.
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