HEALTH / BODY COMPOSITION
Body Fat Calculator
Estimate body fat percentage, fat mass, lean mass, and BMI from a consistent set of adult body measurements.
Set body composition inputs
Use centimetres and measure under the same conditions each time.
Body composition estimate
Your body-fat estimate will appear here
Enter measurements and calculate a screening estimate.
How this body-fat model works
The script uses a U.S. Navy circumference equation, then derives fat mass and lean mass from the estimated percentage. BMI is shown as context only, because BMI and body fat answer different questions.
Measure the same way
Keep posture, tape position, time of day, and hydration as consistent as possible. Repeat a surprising measurement before using it for comparison.
Know the limits
The formula is not a DXA, Bod Pod, skinfold, or clinical assessment. Reference bands are broad and do not account for every age, body shape, or population.
Frequently Asked Questions
What does this body fat calculator estimate?
It estimates body fat percentage, fat mass, lean mass, and BMI from adult measurements using a U.S. Navy circumference method.
Which measurements are required?
Enter age, sex used by the formula, height, weight, waist, and neck. The female version also requires hip circumference.
How should I measure?
Use a flexible tape, keep it level, measure consistently, and repeat the measurement if the number seems unusual. Small technique differences can change the estimate.
Is this a medical diagnosis?
No. This is a screening estimate. It is not a diagnosis and should not replace a qualified assessment or a clinical measurement method.
Why can this differ from another body fat result?
Different methods, tape placement, hydration, body shape, and measurement technique can produce different estimates.