Health & Fitness · Body Composition
Body Fat Calculator
Estimate your body fat percentage with the US Navy circumference method (neck, waist and, for women, hips) or from BMI and age, in metric or imperial units. See your fat and lean mass, where you sit in the ACE body-fat categories, and your waist-to-height ratio.
Your inputs
Quick start — try a typical case
Men: at the navel. Women: at the narrowest point.
Your result Live
Body Fat — Average
19.2%
US Navy circumference method
- Fat Mass
- 15.0 kg
- Lean Body Mass
- 63.0 kg
- BMI-method Estimate (for comparison)
- 21.3%
- Waist-to-height Ratio
- 0.50 — increased health risk
Body-fat categories (men)
5 rowsTape-measure and BMI methods are estimates, typically within 3–4 percentage points of lab methods (DEXA, hydrostatic weighing). Measure in the morning, relaxed, tape snug but not tight.
Population-average estimates for healthy adults, not medical advice. Talk to a doctor or registered dietitian before major changes to diet or exercise, or if you are pregnant or have a health condition.
How this is calculated
Navy (men) %BF = 495 ÷ (1.0324 − 0.19077·log₁₀(waist − neck) + 0.15456·log₁₀(height)) − 450 · (women) 495 ÷ (1.29579 − 0.35004·log₁₀(waist + hip − neck) + 0.221·log₁₀(height)) − 450
- cm
- All circumferences and height in centimetres
- BMI method
- %BF = 1.20 × BMI + 0.23 × age − 10.8 × (1 for men, 0 for women) − 5.4
The US Navy method estimates body density from neck, waist and hip measurements and height, then converts density to body fat with Siri's equation. It needs only a tape measure and is more informative than BMI, because BMI can't tell muscle from fat. The BMI-based formula is shown for comparison.
Assumptions & sources
- Adults; not valid in pregnancy or for very muscular or very lean athletes.
- 1Prediction of percent body fat for U.S. Navy men from body circumferences and height (Hodgdon & Beckett, 1984) — Naval Health Research Center — DTIC ADA143890
- 2Prediction of percent body fat for U.S. Navy women from body circumferences and height (Hodgdon & Beckett, 1984) — Naval Health Research Center — DTIC ADA146456
- 3Body mass index as a measure of body fatness: age- and sex-specific prediction formulas (Deurenberg, Weststrate & Seidell) — British Journal of Nutrition (1991)
Calculator ID HLTH-BODYFAT-001 · version 1.0.0
Common questions
What's a healthy body fat percentage?
Roughly 14–24 % for men and 21–31 % for women falls in the fitness-to-average range. Athletes are often lower; above about 25 % (men) or 32 % (women) is in the obese range.
How accurate is the Navy tape method?
Usually within about 3–4 percentage points of lab methods when measured carefully — good for tracking change over time.