Body Recomposition Change Calculator

About this calculator

Body recomposition — losing fat and gaining muscle at the same time — is easy to miss on a scale because the two changes can roughly cancel out in total weight, even though body composition shifted meaningfully. Tracking it requires two body-composition checks (weight plus body fat percentage, from calipers, a scale with bioelectrical impedance, or a DEXA scan) at two points in time: fat mass = weight × body fat %, and lean mass = weight − fat mass, calculated at both checkpoints and then compared.

Strength coaches and people on a recomposition-focused program (common among beginners and people returning to training after time off, since both fat loss and muscle gain can happen simultaneously at that stage) use this comparison because scale weight alone is a poor progress metric during recomp — someone who lost 4 lbs of fat and gained 3 lbs of muscle only sees a 1 lb change on the scale despite real, meaningful progress.

This calculator takes your before and after weight and body fat percentage and returns exactly how much fat you lost and how much lean mass you gained.