MMA Weight Classes: All 15 Unified Rules Divisions, and How UFC, RIZIN and ONE Differ (2026)

MMA weight classes look promotion-specific, but in North America they all trace back to one document: the Unified Rules of Mixed Martial Arts, maintained by the Association of Boxing Commissions and Combative Sports (ABC). The version amended August 6, 2025 lists 15 weight classes, from atomweight (up to 105 lb) to super heavyweight (over 265 lb).

Most weight-class tables online copy only the UFC's active divisions, or predate the four classes the ABC added in 2017. This page takes the table straight from the ABC's published rules, then explains the part that actually trips viewers up: the same class name means different weights in different promotions.

This site is independent and does not send readers to any promotion or streaming service.

The full 15 Unified Rules divisions (as amended August 6, 2025)

Kilograms are converted at 1 lb = 0.45359237 kg; contracted weights themselves are administered in pounds (as of 2026-08-09).

Why "welterweight is 155–170 lb" is wrong under the current rules

A very common table gives welterweight as "over 155 to 170 lb." Under the current Unified Rules, over 155 to 165 lb is super lightweight, and welterweight starts above 165 lb. The same error shifts light heavyweight: it is over 195 to 205 lb, not 185–205, because over 185 to 195 lb is super middleweight.

The cause is easy to trace. Super lightweight, super welterweight, super middleweight and cruiserweight were added by the ABC in July 2017. Tables written before that never had them, and plenty of articles have been copying those tables ever since.

The UFC does not use all 15

The Unified Rules define which divisions a commission may sanction — not which divisions a promotion must run. The UFC has never adopted the four 2017 additions as standing divisions. So "the UFC's weight classes" and "the Unified Rules weight classes" are not the same list, which is worth remembering whenever a fighter arrives from another promotion and looks unexpectedly large or small for the division.

Striking sports are organised on a different logic entirely: boxing splits into 17 classes, while kickboxing has no unifying body, so both the divisions and the champions differ by promotion. See our boxing weight-class guide and Kickboxing rankings and divisions 2026.

RIZIN sets limits in round kilograms

RIZIN is a Japanese promotion and defines its limits in round kilogram figures rather than pound conversions: flyweight 57 kg, bantamweight 61 kg, featherweight 66 kg, lightweight 71 kg, light heavyweight 93 kg, and women's super atomweight 49 kg (as of 2026-08-09).

Against the Unified Rules featherweight limit of 145 lb (65.8 kg), RIZIN's 66.0 kg gives roughly 200 g of extra room. RIZIN also runs far fewer divisions than the Unified Rules allow, so matchups that fall between them are usually contracted at catchweight.

ONE's class names sit a division heavier

Singapore-based ONE Championship bans cutting weight by dehydration and sets its divisions around a hydrated "walking weight." The effect is that ONE's class names map one step up the Unified Rules ladder:

• ONE flyweight = 135 lb (61.2 kg) → bantamweight under the Unified Rules
• ONE lightweight = 170 lb (77.1 kg) → welterweight under the Unified Rules

Athletes complete a combined hydration test and weigh-in 24 to 48 hours before the event, with hydration measured by a urine specific gravity test. Fail the hydration test and you are not permitted to weigh in at all until you pass it. If neither weight nor hydration clears inside the three-hour testing window, the bout moves to catchweight negotiation, allowed only when both athletes are within 105 percent of each other's official hydrated weight.

What happens when a fighter misses weight

The Unified Rules split this into three cases:

1. Within the division. If both fighters weigh in inside the same contracted division, there is no restriction on the weight difference between them.
2. Weight-miss catchweight. If someone misses the contracted weight and the two end up in different weight classes, the heavier fighter may not exceed the lighter fighter's weight by more than five pounds.
3. Contracted catchweight. When a catchweight is agreed in advance and both fighters come in under it, no spread limit applies — but a commission may refuse the bout if it judges the differential unsafe.

Missing weight is not automatically a cancellation; which of the three cases you land in decides what happens next.

More on the rules

KO and TKO, P4P, decision types and other basics are collected in the combat sports glossary. For how rounds are actually scored, see How MMA scoring works: the 10-point must system and Plan A/B/C.