Fitness & Health

Lean Body Mass Calculator

Estimate lean mass, fat mass, and target weight from body fat.

Inputs

Adjust the assumptions to match your scenario. Results update instantly.

Body weightCurrent body weight in kilograms used to split lean and fat mass.Body fat percentCurrent body fat percentage used to estimate lean mass and fat mass.Target body fatTarget body fat percentage used to estimate target body weight with lean mass held constant.

Results

Primary outputs and comparison insights are built from the current inputs.

Lean mass

63.96

Estimated lean body mass after body fat is removed from total weight.

Fat mass

18.04

Estimated body fat mass in kilograms from the current body fat percentage.

Target weight

75.25

Estimated body weight if lean mass stays constant and body fat reaches the target level.

How this calculator works

The Lean Body Mass Calculator helps you estimate lean mass, fat mass, and a target body weight from current body weight and body fat percentage. Enter body weight, body fat percent, and target body fat to estimate lean mass, fat mass, and target weight. The calculator updates instantly and adds a comparison table plus chart so you can test the sensitivity of the result before you use it in a decision.

Quick guide

Jump straight to the section you need, then return to the calculator.

Inputs Outputs Assumptions Tips Formulas Examples Reference table Visual breakdown References

Inputs

Current body weight in kilograms used to split lean and fat mass.
Current body fat percentage used to estimate lean mass and fat mass.
Target body fat percentage used to estimate target body weight with lean mass held constant.

Outputs

Estimated lean body mass after body fat is removed from total weight.
Estimated body fat mass in kilograms from the current body fat percentage.
Estimated body weight if lean mass stays constant and body fat reaches the target level.

Assumptions

Lean mass is assumed to stay constant when the target body weight is estimated.
Body fat percentage is treated as one current measurement rather than a range.

Tips

Use the calculator for trend planning rather than treating one body-fat reading as perfect.
Target body weight is more useful when paired with a realistic time horizon and training plan.

Formula guide

Use these formulas to audit the output or explain it to someone else.

2 formulas

Fat Mass = Body Weight * Body Fat Percent

Lean Mass = Body Weight - Fat Mass

Usage examples

Review a ready-made scenario, copy it, then tweak inputs to match your case.

Example

3 inputs3 outputs

Recomposition target

Inputs

Example input Body weight: 90
Example input Body fat percent: 24%
Example input Target body fat: 16%

Outputs

Example result Lean mass: 68.4
Example result Fat mass: 21.6
Example result Target weight: 81.43

Lean-mass estimates work best when you compare a current composition reading with a realistic target instead of chasing scale weight alone.

Body composition by body fat percent

5 of 5 rows

Body fat percent	Lean mass	Fat mass
17%	68.06	13.94
20%	65.6	16.4
22%	63.96	18.04
24%	62.32	19.68
27%	59.86	22.14

Small body-fat changes can move the composition estimate meaningfully, so compare a few plausible measurement outcomes before using the result.

Fat mass sensitivity

Highest: 27% (22.14)Lowest: 17% (13.94)

Sort

Body fat percentFat mass

Focus point

17%

13.94

Position

#1 of 5

Original order

Share of total

15.45%

Total: 90.2

PositiveNegative

Small body-fat changes can move the composition estimate meaningfully, so compare a few plausible measurement outcomes before using the result.

References

Body composition planning with lean mass and fat mass estimates
Weight-target estimates based on body fat percentage

FAQ

Common questions

What does the Lean Body Mass Calculator do?

What inputs do I need?

Typical inputs include Current body weight in kilograms used to split lean and fat mass., Current body fat percentage used to estimate lean mass and fat mass., Target body fat percentage used to estimate target body weight with lean mass held constant..

How are the results calculated?

We follow the formulas and assumptions outlined in the "How this calculator works" section. You will see outputs like Estimated lean body mass after body fat is removed from total weight., Estimated body fat mass in kilograms from the current body fat percentage., Estimated body weight if lean mass stays constant and body fat reaches the target level..