Body Fat Calculator
Estimate your body fat percentage from a few tape measurements using the US Navy method, see which category it falls in, and find out how much of your weight is fat and how much is everything else.
Fill in the fields to see your result.
What this actually measures
Your weight tells you how much of you there is. It says nothing about what you are made of. Two people at the same height and weight can carry completely different amounts of fat, muscle and bone, and only one of those three is worth reducing.
This calculator uses the US Navy circumference method, developed in the 1980s so that a fleet of people could be assessed with nothing but a tape measure. It works on a simple observation: for a given height, the circumference of your waist and neck tracks fairly closely with how much fat you are carrying. It is not a scan. It is a good estimate from three measurements and thirty seconds.
The formula
Both equations work in inches and use base-10 logarithms. Metric measurements are converted first.
Once the percentage is known, the rest is arithmetic: fat mass is your weight multiplied by that percentage, and lean mass is whatever is left. Lean mass is the more useful number to watch when you are dieting, because losing it is the thing you are trying to avoid.
What the categories mean
| Category | Men | Women |
|---|---|---|
| Essential fat | 2–5% | 10–13% |
| Athletes | 6–13% | 14–20% |
| Fitness | 14–17% | 21–24% |
| Average | 18–24% | 25–31% |
| Obese | 25%+ | 32%+ |
These bands come from the American Council on Exercise. The gap between men and women is not a rounding difference — women carry substantially more essential fat for reasons of basic physiology, and comparing the two sets of numbers directly is meaningless.
Measuring properly
Almost all the error in this method comes from the tape, not the equation. A centimetre of slack on the waist can move the result by more than a percentage point. Use a flexible tape, keep it level, rest it against the skin without compressing it, and breathe out normally rather than holding your breath or pulling your stomach in.
Measure first thing in the morning before eating, and take each measurement twice. If the two readings disagree by more than half a centimetre, take a third. Then do exactly the same thing next time — consistency matters more than precision, because what you are really watching is the direction of travel.
Why there are two numbers
If you enter your age, the result also shows a second estimate calculated from your BMI using the Deurenberg equation. It uses completely different inputs, so when the two land close together you can be reasonably confident. When they disagree by a lot, it usually means your build is unusual in some way — heavily muscled, or carrying fat somewhere the tape does not reach — and the Navy figure is the one to trust.
Common questions
How accurate is the US Navy body fat method?
For most people it lands within about 3 to 4 percentage points of a DEXA scan, which is good enough to track a direction over time. It is less reliable at the extremes — very lean or very heavy — and it assumes a fairly typical fat distribution. Measure carefully and compare like with like.
Where exactly do I measure my waist?
At the navel for men, and at the narrowest point of the torso for women. Stand relaxed, breathe out normally, and keep the tape level all the way round without pulling it tight. Do not suck in. Measuring in the same place each time matters more than finding the perfect spot.
Why does the calculator ask women for a hip measurement?
The Navy formula uses different inputs for men and women because fat is distributed differently. The women's equation needs waist plus hip minus neck to work, so the hip measurement is not optional for it.
What is a healthy body fat percentage?
Broadly, 14 to 24 percent for men and 21 to 31 percent for women is considered a normal healthy range by the American Council on Exercise. Below the essential fat threshold — around 2 to 5 percent for men and 10 to 13 percent for women — the body cannot function properly.
Is body fat percentage better than BMI?
It answers a more useful question. BMI only knows your weight and height, so a muscular person reads as overweight. Body fat percentage at least tries to separate fat from everything else. A tape measure estimate is still an estimate, but it is a more honest one.
How often should I measure?
Every two to four weeks is plenty. Body fat changes slowly, and measurement error between sessions is large enough that weekly numbers mostly show noise. Measure at the same time of day, under the same conditions, and watch the trend rather than any single reading.
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Please note: CalcuLane gives estimates for general information only and is not medical advice, a diagnosis or a treatment plan. These figures are population averages and cannot account for your individual circumstances. Always speak to a doctor or qualified health professional about your own health.