Most calculators multiply protein by your total body weight. That works for average people, but it quietly inflates the number for anyone with high body fat. Scaling to lean body mass gives a target that matches the tissue that actually needs protein.
The lean-mass formula
Lean body mass is your weight minus fat:
Lean mass (kg) = weight × (1 − body fat %)
Example: 90 kg at 30% body fat → 90 × 0.70 = 63 kg lean mass
Two people, two answers
Set protein with the usual 2.0 g/kg of body weight and you get 180 g for a 90 kg person. Set it from 63 kg of lean mass and you land near 145 g — an easier, more realistic daily target that still protects muscle. The heavier your body fat, the wider that gap becomes.
| Body | 2.0 g/kg (weight) | 2.3 g/kg (lean mass) |
|---|---|---|
| 75 kg, 15% BF | 150 g | 147 g |
| 90 kg, 30% BF | 180 g | 145 g |
| 100 kg, 40% BF | 200 g | 138 g |
When lean mass matters most
For lean athletes the two methods nearly agree, so the choice is cosmetic. For heavier lifters, beginners cutting down, or anyone carrying significant fat, lean-mass protein is the difference between a sustainable plan and an impossible daily grind.
Getting your body fat number
You do not need a lab. A skinfold call, a smart scale, or even a careful estimate within a few percent is enough — precision beats perfection. If you genuinely do not know, leave the field blank and the calculator falls back to total weight.
More muscle does not need more protein set to body fat; fat only adds weight to the scale, not to the requirement.
Enter your body fat in the macro calculator and watch the protein target adjust to your real build.