How to use the Body Fat Calculator
- Measure your neck just below the larynx, and your waist at the navel (men) or at its narrowest point (women). Women also measure the widest part of the hips.
- Enter your height, weight and measurements.
- Read your body fat percentage, category, fat mass and lean mass.
- Optional: compare how a small waist-measurement difference changes the estimate.
The US Navy method
The US Navy formula estimates body fat from height and circumference measurements, because fat around the waist relative to the neck tracks overall body fat well. For men: %BF = 495 ÷ (1.0324 − 0.19077 × log₁₀(waist − neck) + 0.15456 × log₁₀(height)) − 450, with measurements in cm. Women add the hip measurement. It is typically within 3–4 percentage points of laboratory methods such as DEXA.
Body fat categories (American Council on Exercise)
| Category | Women | Men |
|---|---|---|
| Essential fat | 10–13% | 2–5% |
| Athletes | 14–20% | 6–13% |
| Fitness | 21–24% | 14–17% |
| Average | 25–31% | 18–24% |
| Obese | 32%+ | 25%+ |
Measuring tips
- Measure in the morning, before eating, with relaxed (not sucked-in) muscles.
- Keep the tape level and snug but not compressing the skin.
- Take each measurement twice and use the average.
Frequently asked questions
How accurate is the Navy body fat method?
For most people it is within about 3–4% of DEXA scans, but it can be less accurate for very muscular or very lean people.
What is a healthy body fat percentage?
Roughly 21–31% for women and 14–24% for men, according to ACE categories.
Why does BMI differ from body fat?
BMI only uses height and weight, so it cannot tell muscle from fat. Body fat percentage measures composition directly.