How the body fat calculator works
The calculator uses the US Navy circumference method (Hodgdon and Beckett), which estimates body fat from height and a few tape measurements. In centimetres:
- 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
If you also enter your weight, the calculator splits it into fat mass and lean mass (everything that isn’t fat: muscle, bone, organs and water).
How to measure properly
- Measure in the morning, before eating, relaxed and standing tall.
- Use a soft tape measure flat against bare skin. Snug, not squeezing.
- Take each measurement twice and use the average.
- Re-measure every 2–4 weeks under the same conditions to track progress.
ACE body fat categories
| Category | Men | Women |
|---|---|---|
| Essential fat | 2–5% | 10–13% |
| Athletes | 6–13% | 14–20% |
| Fitness | 14–17% | 21–24% |
| Average | 18–24% | 25–31% |
| Above average | 25%+ | 32%+ |
Essential fat is the minimum your body needs to function. Going below these levels is unhealthy.
Using your result
- Losing fat? Keep protein high with the protein calculator and lift weights, so your lean mass stays the same while fat mass drops.
- Building muscle? Watch that body fat rises slowly. A small surplus keeps fat gain low.
- Track the trend. A 1–2% change over a few months is real progress, even if the scale barely moves.
Limitations
Tape-based formulas are estimates. They can be less accurate for very lean, very muscular or very overweight people. Lab methods such as DEXA are more precise. This tool is for adults and does not provide medical advice.
