Competition Weight Calculator
Making a lower weight class through a combination of long-term fat loss and a short-term water cut is a strategy used by competitive strength, combat, and throwing athletes. The key to doing this safely is knowing exactly how much you need to lose, how much time you have, and how much of the cut should come from fat loss versus short-term water manipulation. This calculator takes your current body weight, target weight class, weeks until competition, and days until weigh-in to produce a weekly fat-loss target, safe water cut amount, required daily caloric deficit, and rehydration volume needed after weigh-in.
Competition weight cut formula
Total to lose = Current weight - Target class limit
Max water cut = Current weight x 0.05 (5% limit)
Fat loss required = Total to lose - Water cut (min 0)
Weekly fat loss = Fat loss / Weeks until competition
Daily deficit = Weekly fat loss x 7700 / 7 (7700 kcal per kg fat)
Rehydration = Water cut x 1.5 L/kg (standard protocol)
Frequently asked questions
How much weight can I safely cut before competition?
Most sports medicine authorities recommend cutting no more than 5% of body weight via dehydration for combat sports or strength sports. Cuts above 5% impair performance and increase health risk. A 2% cut is considered mild and recoverable within 2 to 4 hours.
What is the difference between fat loss and water cutting?
Fat loss is long-term weight reduction through a caloric deficit over weeks. Water cutting is short-term dehydration to make a lower weight class, with full rehydration before competing. The two approaches serve different purposes and have very different health profiles.
How long does it take to rehydrate after a water cut?
Full rehydration after a 2 to 3% body weight water cut takes approximately 2 to 4 hours with proper electrolyte and fluid intake. A 5% cut may take 4 to 6 hours to fully restore plasma volume. Weigh-in windows of 2 hours are insufficient for full recovery from large cuts.
What is a realistic rate of fat loss?
A safe rate of fat loss is 0.5 to 1% body weight per week, or 0.5 to 1 kg per week for most athletes. This requires a daily caloric deficit of approximately 500 to 1000 kcal. Losing weight faster than this risks muscle loss and performance decrements.
Should I cut weight for my first competition?
For your first competition, compete at your natural body weight in whichever class you currently fall into. Learning competition procedures, warm-up strategy, and performance execution is more valuable than optimising weight class placement. Weight cutting strategies can be added once you have competition experience.
Official sources
- National Strength and Conditioning Association: NSCA Weight Management for Sport.
- American College of Sports Medicine: ACSM Weight Loss for Athletes.
Reviewed by the CalculatorHub team, edited by James Graham, 14 June 2026. See our methodology.