Weight Cut Calculator

A weight cut is how an athlete gets down to a weight class limit for an official weigh-in. It has two parts: gradual loss of body fat over weeks, and acute weight loss in the final days, which mostly comes from gut content, stored carbohydrate and body water¹ ². This calculator splits your total cut between those two parts and checks the acute part against published limits.

What a Weight Cut Plan Measures

It measures how much you need to lose, how much of that could come off gradually before fight week, and how much would be left for the last 7 days. It is built for adult boxers, MMA fighters, wrestlers, judo and BJJ athletes, and powerlifters. It does not give fight-week methods, fluid plans or calorie targets.

The Formula

Total to lose = current weight - target weight

Weeks of gradual loss = (days until weigh-in - 7) / 7

Weight at start of fight week = current weight x 0.99^weeks (never below your target)

Acute loss = weight at start of fight week - target weight

Acute loss percent = acute loss / target weight x 100

The 1 percent weekly cap and the acute limits come from the Australian Institute of Sport's making weight decision tree, which is based on a 2017 review of weight making in Olympic combat sports¹ ².

How This Calculator Computes Your Result

Enter your age, current weight, target weigh-in weight, days until weigh-in and how long you have between weigh-in and competing, in pounds or kilograms. The tool keeps the last 7 days as fight week and assumes you lose up to 1 percent of body weight per week before that, with the slower 0.5 percent pace shown for comparison.

You get your total cut, the weekly pace you would need, your projected weight when fight week starts and what is left for fight week. If that is too much, it shows the lowest target your timeline supports and how many days you would need. Weights and percents are rounded to 0.1. The lowest target is rounded up, so it stays within the limit.

For example, a 170 lb (77.1 kg) fighter with 70 days to make 155 lb (70.3 kg) needs to lose 8.8 percent of body weight. At 1 percent a week for 9 weeks, he could reach about 155.3 lb, leaving 0.3 lb for fight week.

What Your Result Means

The acute part is rated by how far above your target you would be when fight week starts¹:

The 5 and 3 percent limits come from the AIS decision tree, which advises athletes over them not to compete at that weight and, if already lean, to move up a weight class¹. The 3 percent line matches a 2021 American College of Sports Medicine (ACSM) consensus: acute losses of about 2 to 3 percent are likely to have few disadvantages, but larger ones may harm health and performance³.

How to Weigh Yourself for This Plan

Use your morning weight. Weigh after waking and using the toilet, before eating or drinking, on the same scale each time¹. Daily weight can swing by a kilogram or more from food and water, so track your trend over a week rather than one reading.

Why Gradual Loss Should Do Most of the Work

A slower pace protects muscle and strength. In a study of 24 elite athletes, those who lost about 0.7 percent of body weight per week gained 2.1 percent lean mass, while those who lost about 1.4 percent per week did not⁴. The authors suggest about 0.7 percent per week for athletes who want to keep or build strength while losing weight⁴. That is why this tool caps the gradual phase at 1 percent per week.

Gradual loss only works if you have body fat to lose. The AIS tree treats about 5 percent body fat for men and 12 percent for women as the point where moving up a class makes more sense than more fat loss¹.

Why Weight Cutting Rules Exist

In November and December 1997, three college wrestlers aged 19 to 22 died while trying to lose weight fast before competing⁵. The NCAA then changed its rules³ ⁵. Today, each college wrestler has a lowest allowed weight set from body fat testing, and planned loss is capped at 1.5 percent of body weight per week⁶. Wrestlers must also pass a hydration test, with a urine specific gravity of 1.020 or lower⁶. Note that 1.5 percent is a rule ceiling, not a target.

Professional MMA has moved the same way. After a fighter's death in 2015, ONE Championship changed its weigh-in rules³. It now runs a combined hydration test and weigh-in 24 to 48 hours before each event, and an athlete who fails the hydration test is not allowed to weigh in⁷.