Body Fat Percentage Calculator
Body fat from a tape measure, with fat and lean mass.
The equations were fitted separately for men and women, so they need one of the two. It is the body the formula describes, not an identity.
Just below the Adam's apple, the tape sloping slightly down to the front. Don't flare the neck.
Men: level with the navel. Women: at the narrowest point. Relaxed, after breathing out — not pulled in.
Fill in the fields and the answer appears here.
An estimate from a formula, not a measurement. It does not replace a doctor, a dietitian or a qualified trainer — least of all with a health condition, during pregnancy or breastfeeding, or under 18.
How this was worked out
Fill in the fields and the answer appears here.
Guide: Body fat with a tape measure4 min read
Body fat with a tape measure
The U.S. Navy developed this method in the 1980s to assess thousands of people without laboratory equipment: height and three circumferences — neck, waist and, for women, hips — go into an equation that estimates body density, and body fat follows from it. An ordinary tape measure is all it takes.
The answer comes with fat mass and lean mass in kilograms or pounds, because a percentage is abstract and a kilogram is not.
How to measure
Neck: just below the Adam’s apple, the tape sloping slightly down to the front, neck relaxed. Waist: level with the navel for men and at the narrowest point for women, standing relaxed after breathing out — not pulled in. Hips, women only: at the widest point of the buttocks, feet together.
Snug, without pressing into the skin. Take each measurement three times and use the average; first thing in the morning, before eating, is the most repeatable time.
How far to trust it
Against laboratory scans the method is usually within about 3.5 percentage points, and further off at the extremes. That is why the page shows a likely range beside the number. Where it shines is the trend: measured the same way each time, the change over months says more than any single reading.
Reference ranges, without labels
The page lists the American Council on Exercise’s ranges for your sex — essential fat, athletes, fitness, average and above average — to compare against, not as a judgement. Essential fat is the minimum for the body to work, and staying there for long is a health risk of its own. Where anyone should sit depends on age, sport and health, which a tape cannot see.
With lean mass known, the TDEE calculator can use the Katch-McArdle equation, usually the better one for people who train; the link under the answer carries the number there. Nothing you type is sent anywhere.
How we calculate
U.S. Navy (Hodgdon & Beckett) (1984)
Men: 495 ÷ (1.0324 − 0.19077 × log₁₀(waist − neck) + 0.15456 × log₁₀(height)) − 450. Women: 495 ÷ (1.29579 − 0.35004 × log₁₀(waist + hip − neck) + 0.22100 × log₁₀(height)) − 450. All in centimetres.
Source: Hodgdon JA, Beckett MB. Prediction of percent body fat for U.S. Navy men and women from body circumferences and height. Naval Health Research Center, San Diego; Reports 84-11 and 84-29; 1984. Metric form of the equations.
Reference ranges
Essential fat, athletes, fitness, average and above average, with the ACE's limits for each sex. The names are this page's: the ACE calls the top range something else, and here no range carries a judgement.
Source: American Council on Exercise (ACE), body fat percentage reference ranges.
Frequently asked questions
How accurate is the U.S. Navy body fat method?
Against a laboratory scan it is usually within about 3.5 percentage points, and further off at the extremes of very lean or very heavy bodies. That is why the page shows a likely range beside the number. Measured the same way each time, it is good at showing a trend.
Where do I measure my neck, waist and hips?
Neck just below the Adam's apple. Waist level with the navel for men and at the narrowest point for women, relaxed after breathing out. Hips, for women only, at the widest point of the buttocks. Tape snug but not pressing, and each measurement three times.
What is a normal body fat percentage?
The American Council on Exercise's reference ranges, which the page lists for your sex, put the fitness range at 14–17% for men and 21–24% for women, and the average range at 18–24% and 25–31%. They are for comparison, not a verdict: where anyone should sit depends on age, sport and health.
What is lean mass?
Everything that is not fat: muscle, bone, organs, water. The calculator subtracts the estimated fat mass from your weight. Lean mass is what the Katch-McArdle equation in the TDEE calculator uses, and the link under the answer takes it there.
Why does it need my hips if I am a woman?
Because the Navy fitted separate equations for men and women, and the women's adds the hip measurement, where more fat is carried. The men's equation uses the waist and neck only.
Is it better than BMI?
It answers a different question. BMI compares weight with height and cannot tell muscle from fat; the tape method estimates how much of the weight is fat. Both are estimates, and neither is a diagnosis.
Are my measurements stored?
No. They are used in this tab and gone when it closes; nothing is sent anywhere.