Lean Body Mass Calculator
Estimate lean body mass and fat mass from US Navy tape measurements, height and waist (RFM), or a body fat percentage you already know.
Published by Reeve Editorial Team · Methods and sources updated
Estimated lean body mass
44.8 kg
Everything that is not fat: muscle, water, organs, and bone.
Estimated fat mass
25.2 kg
Body fat · RFM method
36.0%
Inputs stay in this tab. Saving keeps a copy on this device until you reset or clear it.
These adult screening estimates do not apply during pregnancy. Body composition, ancestry, age, medical history, and measurement technique can change how a result should be interpreted.
How this tool works
Lean body mass = body weight − fat mass, where fat mass = weight × body fat %. Choose how body fat is estimated: the US Navy circumference equations (Hodgdon & Beckett, 1984), the Relative Fat Mass equation (Woolcott & Bergman, 2018), or a percentage from another assessment such as a scan.
Lean mass includes muscle, water, organs, and bone, so it is not the same as muscle mass. Any error in the body fat estimate carries into the lean mass result. Compare results from the same method over time.
Sources
Frequently asked questions
Is lean body mass the same as muscle mass?
No. Lean body mass is everything that is not fat, including water, organs, and bone as well as muscle. Muscle makes up only part of it.
How can I use lean body mass?
Some people use it to follow body composition during a diet or training phase, or to put a protein target in context. Look at the trend from one consistent method rather than a single result.
Which method is most accurate?
A body fat percentage from a validated scan is usually more precise than tape-based equations, but every method has error. The tape methods here are convenient population estimates.