Body Fat & BMI Calculator
Measure body fat percentage with the U.S. Navy method, calculate BMI, and see fat mass, lean mass and healthy ranges. All runs in your browser.
Your measurements
Results
BMI
24.5
Normal
Body fat
10.6%
Athletic
Fat mass
8.0 kg
Lean mass
67.0 kg
Ideal body fat range
8–19%
Common healthy band for Male: 8–19%
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Features
- BMI with WHO health category
- U.S. Navy body fat formula
- Fat mass & lean mass breakdown
- Age-based ideal body fat range
- Metric / imperial switching + CSV export
Frequently asked questions
How the maths works
The U.S. Navy circumference method estimates body fat from tape measurements, and BMI classifies weight against height. Neither requires a special device — just a tape measure and a scale.
- 1Calculate BMI: weight (kg) divided by height (m) squared.
- 2Convert height, waist, neck (and hip for women) to inches.
- 3Male body fat % = 495 / (1.0324 − 0.19077·log10(waist−neck) + 0.15456·log10(height)) − 450.
- 4Female body fat % = 495 / (1.29579 − 0.35004·log10(waist+hip−neck) + 0.22100·log10(height)) − 450.
Tape estimates are approximate; body fat varies with hydration and measurement technique. Results are educational, not a medical diagnosis.
Everything you need to know
What is body fat percentage?
Body fat percentage is the share of your total weight made up of fat tissue. The rest — muscle, bone, organs and water — is your lean mass.
The U.S. Navy method estimates the percentage from circumferences, so you can track composition changes without a body-fat scale or impedance device.
BMI vs body fat: why both?
BMI is a quick weight-for-height screen, but it cannot tell muscle from fat — a muscular athlete can read "overweight" while carrying little fat.
Body fat percentage fills that gap. Checking both gives a more honest picture of your health and your progress.
Related calculators
Body composition scenarios
Jump to a pre-filled example, or start from scratch.
U.S. Navy Body Fat Formula Calculator
The tape-measure method used by the military — no scales that estimate, just waist, neck and height.
BMI vs Body Fat Percentage — Why They Disagree
When muscle inflates BMI but body fat stays healthy — the case for measuring both.
Female Body Fat Calculator
The female Navy formula adds the hip measurement — a more accurate picture for women.
Ideal Body Fat Percentage by Age
Healthy body fat is a moving target — see how the ideal band shifts by age.
Average Body Fat Percentage for Men
A realistic male starting point — what "average" actually reads on the Navy scale.
BMI Calculator — Weight & Height
The most-asked health number — weight vs height — plus the body-fat context.
Lean Mass & Body Composition
A low-fat, high-lean profile — see fat mass versus lean mass side by side.
Weight Loss — Body Fat Target
Know where you start before you cut — fat mass, lean mass and the range to aim for.