Body Fat Calculator (US Navy Method)
Estimate your body fat percentage with just a tape measure — no calipers or scans needed. This uses the US Navy circumference method, accurate to within about 3–4% for most people, and tells you which body fat category you fall into.
How to use this calculator
- Measure your neck just below the Adam's apple, keeping the tape level.
- Measure your waist — men at the navel, women at the narrowest point. Don't suck in.
- Women: also measure hips at the widest point.
- Enter height and measurements in cm, then press Calculate to see your body fat percentage and category.
Formula used
Women: BF% = 495 / (1.29579 − 0.35004·log₁₀(waist+hip−neck) + 0.22100·log₁₀(height)) − 450. All measurements in centimeters. Developed by the US Naval Health Research Center and used in military fitness assessments.
Example calculation
A man, 175 cm, neck 38 cm, waist 85 cm:
waist − neck = 47 → BF% = 495 / (1.0324 − 0.19077·log₁₀(47) + 0.15456·log₁₀(175)) − 450 ≈ 16.9% — within the "fit" range.
What is body fat percentage?
Body fat percentage is the share of your total weight that is fat tissue — a far more meaningful health and fitness measure than weight or BMI, because it separates fat from muscle, bone and water. Two people with identical BMIs can have wildly different body compositions.
Some fat is essential (hormones, insulation, organ protection): about 3% minimum for men and 12% for women. Health risk rises mainly with visceral fat around the abdomen — which is exactly what the waist measurement in this method captures, making it a surprisingly good proxy despite needing only a tape measure.
Why use this calculator?
- Track fat loss properly — the scale can't tell whether you lost fat or muscle; this can.
- Get a lab-free estimate anywhere with just a tape measure, using a military-validated method.
- See honest category ranges instead of chasing unrealistic physique numbers from social media.
Frequently asked questions
How accurate is the Navy body fat method?
Studies put it within about 3–4% of DEXA scan results for most body types — comparable to consumer bioimpedance scales and much better than BMI. Its accuracy drops for very muscular or very lean individuals. Measure at the same time of day and track the trend.
What is a healthy body fat percentage?
Per American Council on Exercise ranges: men — athletes 6–13%, fit 14–17%, average 18–24%; women — athletes 14–20%, fit 21–24%, average 25–31%. Women naturally carry more essential fat, so the ranges differ by design.
How do I measure correctly?
Use a flexible tape, keep it level and snug but not compressing the skin, and breathe normally. Measure the waist without sucking in — honest measurements are the whole point. Take each measurement twice and average.
How fast can I lower my body fat percentage?
A sustainable pace is losing 0.5–1% of body fat per month through a moderate calorie deficit and strength training. Faster drops usually include muscle loss, which worsens the very ratio you're trying to improve.