Body Fat Calculator
Estimate your body fat percentage with the US Navy method using waist, neck and hip measurements, in metric or imperial units.
Body Fat Calculator — input your values
What does this health calculator do?
This calculator estimates your body fat percentage using the US Navy circumference method, which relies on height plus waist, neck and hip measurements. It works in both metric and imperial units and includes a weight input so you can see your estimated fat mass and lean mass in kilograms or pounds.
Your result is compared against the standard body fat categories for your sex — essential fat, athletes, fitness, average and obese — so you can see where you fall and how much of your body weight is lean tissue. Body fat percentage is generally more informative than BMI alone.
Please note this is an estimate for general wellness purposes and is not medical advice. For a clinical body composition measurement, see a qualified professional.
Formula and variables
Women: 495 / (1.29579 − 0.35004·log₁₀(waist + hip − neck) + 0.22100·log₁₀(height)) − 450.
| Symbol | Meaning |
|---|---|
| waist | Waist circumference in inches |
| neck | Neck circumference in inches |
| height | Height in inches |
Worked example
A man with height 175 cm, weight 75 kg, waist 85 cm and neck 38 cm.
- Convert to inches: height = 68.9 in, waist = 33.5 in, neck = 15.0 in.
- Gap = 33.5 − 15.0 = 18.5 in.
- log₁₀(18.5) = 1.2672, log₁₀(68.9) = 1.8382.
- Body fat % = 495 ÷ (1.0324 − 0.19077 × 1.2672 + 0.15456 × 1.8382) − 450 ≈ 18.4%.
Answer: Body fat ≈ 18.4% — the fitness category.
Tips and common mistakes
Tips
- Measure the waist at the navel and the neck just below the larynx for consistent, repeatable results.
- Take measurements first thing in the morning, before meals and without tight clothing.
- Trends matter more than single readings — track monthly changes rather than daily swings.
- Combine the estimate with strength and energy levels; the numbers are a guide, not a verdict.
Common mistakes to avoid
- Pulling the tape tight — keep it snug but not compressing the skin.
- Using the women's formula for men or skipping the hip measurement, which is required for women.
- Treating the estimate as exact; circumference methods can deviate by several percentage points from lab results.
Body Fat Calculator — frequently asked questions
How accurate is the US Navy body fat method?
It typically agrees with lab methods such as DEXA within about 3 percentage points for most people. Consistency in measurement technique matters more than the formula choice.
What is a healthy body fat percentage?
For men, essential fat is under 6%, athletes range from 6 to 13%, fitness from 14 to 17% and average from 18 to 24%. For women the equivalent ranges are under 14%, 14 to 20%, 21 to 24% and 25 to 31%.
Do I need the hip measurement as a man?
No — the male Navy formula only uses waist, neck and height. Hip is only required for the female formula.
Why is body fat percentage better than BMI?
BMI can't distinguish muscle from fat, so muscular people can look overweight. Body fat percentage directly estimates the fat portion of your weight.
How should I measure my waist?
Stand relaxed, wrap the tape around your bare waist at navel level, and read the value after a normal exhale without pulling the tape tight.
Can body fat change quickly?
Day-to-day changes are mostly water. Meaningful fat loss or gain shows up over weeks, so measure on the same schedule rather than every day.