Body Fat Calculator
Body fat percentage tells you something BMI cannot: how much of your weight is fat rather than muscle. This calculator uses the US Navy circumference method, which needs nothing more than a tape measure.
Formula
Men: %BF = 495 ÷ (1.0324 − 0.19077·log₁₀(waist − neck) + 0.15456·log₁₀(height)) − 450
- Women add the hip measurement to the waist term
- All measurements in the same unit; the US Navy method uses inches
It is a circumference estimate, so measure at the same points each time
What to Measure
The Navy method uses body circumferences rather than skinfolds:
- Men: height, neck and waist (at the navel)
- Women: height, neck, waist (at the narrowest point) and hips (at the widest)
Measure on bare skin, keep the tape level and snug without compressing, and take each reading two or three times to average out error.
Typical Ranges
Commonly cited ranges for adults:
- Men: essential 2–5%, athletic 6–13%, fit 14–17%, average 18–24%, above 25% considered high
- Women: essential 10–13%, athletic 14–20%, fit 21–24%, average 25–31%, above 32% considered high
Women carry more essential fat than men for normal physiological function, which is why the ranges differ.
Accuracy and Better Alternatives
The Navy method typically lands within about 3–4 percentage points of a DEXA scan, which is respectable for a tape measure but not precise. Its real strength is consistency: measured the same way each time, it tracks change reliably even if the absolute number is a little off.
For genuine precision, DEXA and hydrostatic weighing remain the reference methods.
Quick Reference
| 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% and over | 32% and over |
Frequently Asked Questions
- Is body fat percentage better than BMI?
- For most purposes yes, because it distinguishes fat from muscle. BMI classes many muscular people as overweight; body fat percentage does not.
- How accurate is the Navy method?
- Usually within 3 to 4 percentage points of a DEXA scan. Measurement technique matters more than the formula, so be consistent about tape placement.
- What is a healthy body fat percentage?
- Broadly 14 to 24 per cent for men and 21 to 31 per cent for women, varying with age and athletic background. Very low levels carry their own health risks.
- Why does my result change day to day?
- Hydration, food in the digestive tract and tape placement all shift the waist reading. Measure at the same time of day under the same conditions and compare weekly.