Lean Body Mass Calculator
Find your lean body mass, the fat mass you carry and the weight you would need for a goal body fat percentage.
Recent
Formula
How the calculation works
Enter your body weight, your body fat percentage from a scale or caliper, and the body fat percentage you are aiming for.
The tool multiplies your weight by one minus body fat over 100 to get the lean body mass, then subtracts it to get fat mass.
It divides lean body mass by one minus the goal body fat over 100 to show the weight that goal would imply.
Common mistakes
- Trusting a bathroom scale's body fat reading as exact, because it can be several percentage points off and skews the lean mass figure.
- Aiming for an unrealistically low body fat, since essential fat is about 3 percent for men and 12 percent for women and going lower is unsafe.
When to use it
- Use it to see how much of your weight is muscle and bone rather than fat, which scale weight alone cannot show.
- Use it to set a realistic goal weight for a target body fat percentage before a cutting phase.
Worked example
At 80 kg with 25 percent body fat the lean body mass is 60 kg and the fat mass is 20 kg. To reach 15 percent body fat at the same lean mass you would need to weigh about 70.6 kg.
Common questions
What counts as lean body mass?
Lean body mass is everything in the body except fat, so it includes muscle, bone, organs, water and skin, and it is weight minus fat mass.
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