Body fat calculator
This body fat calculator uses the US Navy tape method: a few circumference measurements, no calipers, no scan. It's not laboratory-accurate, but it's free, repeatable at home, and — the part that matters — consistent enough to track a direction over months.
An estimate for training decisions — not medical advice.
Body fat categories
Typical reference ranges for adults.
| Category | Male | Female |
|---|---|---|
| Essential fat | < 6% | < 14% |
| Athletic | 6–13% | 14–20% |
| Fitness | 14–17% | 21–24% |
| Average | 18–24% | 25–31% |
| Above average | ≥ 25% | ≥ 32% |
How to measure so the number means something
Measure in the morning, before eating, with the tape snug but not compressing. Neck: just below the larynx, tape sloping slightly down at the front. Waist: at the navel for men, at the narrowest point for women. Hip: at the widest point, women only.
Take each measurement twice and use the average. Then measure the same way, at the same time of day, every time — the absolute number is worth much less than the change in it.
What the estimate is good for
The Navy method typically lands within about 3–4 percentage points of a DEXA scan, and it's biased by where you personally store fat. So don't argue about whether you're 14% or 17% — that's inside the error bar.
What it does well is direction. Waist shrinking while bodyweight holds means you're recomposing, and that's a conclusion no scale can give you on its own. Log it monthly alongside your lifts; in Tanko, body fat and weight sync from Apple Health and chart next to your training.
Frequently asked questions
How accurate is the Navy body fat formula?
Roughly ±3–4 percentage points against DEXA for most people, and consistently off in the same direction for any given individual — which is exactly what you want for tracking change.
What is a healthy body fat percentage?
Broadly 10–20% for men and 18–28% for women, with athletes lower. Essential fat — about 3% for men and 12% for women — is the floor, not a target.
Why does my waist measurement change so much?
Food, water and time of day move it by several centimetres. Measure fasted in the morning and only compare like with like.
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