Body Fat Calculator
Estimate your body fat percentage using the U.S. Navy method
Quick Answer
Healthy body fat ranges are 10–20% for men and 18–28% for women. Enter your measurements to get your estimate.
Body Fat Calculator: formula, worked examples and limitations
A complete reference answer — readable without using the calculator.
Definition
Body fat percentage is the share of total body mass made up of fat tissue. The U.S. Navy circumference method estimates it from tape measurements using a log-based regression equation.
What it measures
It estimates total fat mass as a percentage of body weight. It is an estimate from circumferences — not a direct measurement like DEXA or hydrostatic weighing.
Formula
- Men: %fat = 495 ÷ (1.0324 − 0.19077 × log10(waist − neck) + 0.15456 × log10(height)) − 450
- Women: %fat = 495 ÷ (1.29579 − 0.35004 × log10(waist + hip − neck) + 0.22100 × log10(height)) − 450
- All circumferences in centimetres.
Worked examples
Computed with the same engine as the calculator above.
Man, 178 cm
Inputs: waist = 90 cm, neck = 38 cm, height = 178 cm
495 ÷ (1.0324 − 0.19077×log10(90−38) + 0.15456×log10(178)) − 450
20.1% body fat — Acceptable
Woman, 165 cm
Inputs: waist = 75 cm, hip = 96 cm, neck = 32 cm, height = 165 cm
495 ÷ (1.29579 − 0.35004×log10(75+96−32) + 0.22100×log10(165)) − 450
27.9% body fat — Acceptable
| Category | Men | Women |
|---|---|---|
| Essential fat | Below 6% | Below 14% |
| Athletes | 6 – 13.9% | 14 – 20.9% |
| Fitness | 14 – 17.9% | 21 – 24.9% |
| Average | 18 – 24.9% | 25 – 31.9% |
| Obese | 25% and above | 32% and above |
Method
Measurements are converted to centimetres, inserted into the Navy equation for the selected sex, and the result is classified against the category table above.
Limitations
- Accuracy is roughly ±3–4 percentage points versus DEXA, and depends heavily on correct tape placement.
- The equation was derived on military populations and is less accurate at very low or very high body fat.
- It cannot detect where fat is stored, and it is not validated for pregnancy or for people under 18.
Rounding rules
Body fat percentage is displayed with one decimal; categories use the unrounded value.
Evidence level
Established estimation method. The U.S. Navy circumference equation is a published, validated regression, but it typically differs from DEXA by roughly 3–4 percentage points for an individual.
Sources
Method and reference values last reviewed by the SnapBodyCalc editorial team.
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Body Fat Percentage: What It Means and How to Measure ItBody fat percentage is a more accurate indicator of health than weight alone. Learn what the numbers mean, healthy ranges, and how to measure yours accurately.
Read articleRelated Calculators
Frequently Asked Questions
Understanding Body Fat Percentage: Your Complete Guide
Body fat percentage is one of the most meaningful indicators of fitness and health — arguably more useful than BMI for understanding your body composition. Unlike BMI, which only considers weight and height, body fat percentage tells you exactly how much of your body is fat tissue versus lean mass (muscle, bones, organs, and water). Two people with identical BMI can have vastly different body compositions, fitness levels, and health profiles.
The U.S. Navy Method Explained
Our calculator uses the U.S. Navy circumference method, developed by the Naval Health Research Center in the 1980s for assessing military recruits. It estimates body fat by measuring waist, neck, and for women, hips — combined with height. The formula uses logarithmic calculations validated in multiple studies, typically producing results within 3–4% of clinical methods like DEXA scans. This makes it one of the most reliable free estimation techniques available.
Healthy Body Fat Ranges by Gender and Category
For men: essential fat 2–5%, competition athletes 6–13%, fitness level 14–17%, acceptable 18–24%, obese 25%+. For women: essential fat 10–13%, competition athletes 14–20%, fitness level 21–24%, acceptable 25–31%, obese 32%+. Women naturally carry more essential fat for reproductive function. Staying within the "fitness" range is optimal for both health and appearance.
How to Measure Accurately
Waist: Measure at the navel level while standing, after exhaling normally — don't suck in. Neck: Just below the Adam's apple, tape level and perpendicular. Hips (women): Widest point of buttocks. Use a flexible tape, snug but not compressing skin, and always measure at the same time of day for consistency.
Measurement Methods Compared
DEXA scan (±1–2%, $50–150) is the gold standard. Hydrostatic weighing (±1.5–2%) uses underwater density. Bod Pod (±2–3%) uses air displacement. Skinfold calipers (±3–4%) need a trained practitioner. Navy method (±3–4%) is free, requires only a tape measure, and is excellent for tracking trends over time.
Body Fat vs. BMI: Why Both Matter
Our BMI Calculator offers quick screening, but body fat percentage is more informative. A bodybuilder with BMI 28 might have 12% body fat. A sedentary person with BMI 23 could have 30% ("skinny fat"). For the most complete assessment, combine body fat with BMI and our Waist-to-Hip Ratio Calculator.
The Dangers of Very Low Body Fat
Going below essential fat levels (2–5% men, 10–13% women) causes hormonal disruption, weakened immunity, bone density loss, chronic fatigue, and impaired organ function. Competition-level leanness should only be maintained temporarily. Year-round, aim for the fitness or acceptable range for optimal health.
Improving Your Body Composition
To reduce body fat while preserving muscle: create a moderate calorie deficit (300–500 below TDEE), maintain high protein (1.8–2.4 g/kg), and train with resistance 3–4 times weekly. Our Calorie Calculator and Macro Calculator help plan your nutrition. Expect 0.5–1% body fat reduction per month.
Tracking Body Fat Over Time
Measure every 2–4 weeks, not daily. Always use the same conditions — same time of day, hydration state, and clothing. Track monthly trends rather than individual measurements. Body composition changes slowly, and short-term water and food fluctuations obscure true progress.
Your Privacy Matters
All calculations happen in your browser. Your measurements are never sent to any server or stored. SnapBodyCalc is built with privacy first — your health data stays completely private. Analytics and web fonts still make standard requests that include your IP address and the page URL — but never your measurements.