Body Composition Goal Calculator
Find your goal weight for a target body fat percentage while preserving lean mass. Enter your current weight, current body fat, and goal body fat to see your goal weight, the fat you need to lose, and your lean mass.
- Assumes constant lean mass during fat loss.
Formula
Goal weight = lean mass / (1 − goal body fat % / 100), lean mass = weight × (1 − current body fat %/100)
- The calculator assumes you keep your lean mass and lose only fat to reach your goal.
- Lean mass = current weight × (1 − current body fat % ÷ 100).
- Goal weight = lean mass ÷ (1 − goal body fat % ÷ 100).
- Fat to lose is the difference between your current weight and goal weight.
- In practice some lean mass is lost during a cut; resistance training and adequate protein help preserve it.
80 kg at 25% body fat, goal 15%
Inputs
- Current Weight: 80 kg
- Current Body Fat: 25 %
- Goal Body Fat: 15 %
Lean mass = 80 × 0.75 = 60 kg. Goal weight = 60 ÷ 0.85 ≈ 70.6 kg, so about 9.4 kg of fat to lose.
Frequently asked questions
How is goal weight calculated?
It keeps your current lean mass fixed and solves for the weight at which that lean mass equals your target body fat percentage.
Does this assume I keep all my muscle?
Yes. It assumes lean mass stays constant and only fat is lost, which is the ideal case. Real results depend on training and diet.
How do I preserve lean mass while losing fat?
Eat enough protein, keep strength training, and avoid very aggressive calorie deficits so most of the loss comes from fat.
What is a realistic goal body fat?
Healthy ranges are roughly 10–20% for men and 18–28% for women. Very low levels are hard to maintain and not always healthy.
How accurate is this estimate?
It is only as accurate as your body fat measurement. Use a consistent method and treat the goal weight as a target, not a guarantee.
Related calculators
Ideal Body Fat Percentage Calculator Ideal Body Fat Percentage Calculator is a health and wellness calculator that helps you calculate a percentage from a part and a whole, or a percentage change. The formula used is: Healthy body fat ranges are taken from age- and gender-based reference tables.. Enter values using the units shown next to each input field (e.g. kg, cm, years). Body Fat Calculator Popular Estimate your body fat percentage with the US Navy circumference method. Enter your sex, height, and a few tape measurements to see your body fat percentage, category, and healthy range. Weight Loss Percentage Calculator Weight Loss Percentage Calculator is a health and wellness calculator that helps you calculate a percentage from a part and a whole, or a percentage change. The formula used is: Weight Loss % = ((Starting Weight − Current Weight) / Starting Weight) × 100. Enter values using the units shown next to each input field (e.g. kg, cm, years).