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Category Sport Fitness

Current Weight (kg)

Height (cm)

Age (years)

Body Fat % (Approx)

Organization

Sex

Lean Body Mass --

Fat Mass --

Est. Total Water --

Safety Limit:

Class Name	Limit	Cut Required	Difficulty

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About

Weight cutting is a strategic, albeit risky, component of combat sports and weight-class-restricted athletics. For fighters and powerlifters, the goal is to compete in the lowest possible weight class to maximize strength and size advantages against opponents. However, cutting too much weight—specifically through dehydration—can lead to severe health complications, reduced performance, and kidney failure.

This tool acts as a strategic planner for athletes. By analyzing your current walk-around weight, body fat percentage, and lean muscle mass, it calculates a "Safe Floor" for weight cutting. It estimates total body water and provides a breakdown of how much weight can be acutely cut via dehydration (water manipulation) versus how much must be lost through fat reduction (diet/caloric deficit) to make a specific class in the UFC, IBA, or IPF.

Formulas

The calculator estimates Lean Body Mass (LBM) and Total Body Water (TBW) to determine the Maximum Safe Dehydration limit (typically capped at 5-8% of total body weight for professionals).

LBM = Weight × (1 − BodyFat)

We estimate Total Body Water based on the Watson Formula for athletes:

TBW = 2.447 − 0.09156Age + 0.1074Height + 0.3362Weight

The Minimum Safe Weight (MSW) assumes a maximum acute water loss of Limit%:

MSW = Weight − (Weight × Limit)

Reference Data

Organization	Class Name	Weight Limit (lbs)	Weight Limit (kg)	Recovery Limit
UFC (MMA)	Flyweight	125 lbs	56.7 kg	None
UFC (MMA)	Bantamweight	135 lbs	61.2 kg	None
UFC (MMA)	Lightweight	155 lbs	70.3 kg	None
IBA (Boxing)	Cruiserweight	189.6 lbs	86 kg	Strict Weigh-in
IBA (Boxing)	Heavyweight	202.8 lbs	92 kg	Strict Weigh-in
IPF (Powerlifting)	Class 59	130.1 lbs	59 kg	2-Hour Weigh-in
IPF (Powerlifting)	Class 93	205 lbs	93 kg	2-Hour Weigh-in
ONE Championship	Hydration Test	Varies	Varies	Fail if Urine SG > 1.025

Frequently Asked Questions

Fat loss is a chronic process achieved through a caloric deficit over weeks or months. Water cutting is an acute process done 24-48 hours before weigh-ins, removing water from the body (sweat, urine). Water weight returns immediately after rehydration, whereas fat loss is sustained.

Most sports science guidelines suggest that losing more than 5% of your body weight via dehydration drastically increases the risk of performance decline and health issues. Elite fighters often push this to 8-10%, but this requires professional medical supervision.

Different federations have different weight classes. For example, a 'Middleweight' in MMA (185 lbs) is different from a 'Middleweight' in amateur boxing (75kg / 165 lbs). This tool contains the specific limits for each major organization.

Weigh-in timing (24-hour vs. 2-hour) is critical. The tool highlights risks based on the standard. For 2-hour weigh-ins (like IPF), large water cuts are dangerous because there is insufficient time to rehydrate.