Body Fat % Calculator — US Navy Circumference & BMI Formula Methods
Enter height, weight, age, and circumferences to estimate body-fat percentage using the US Navy circumference method or the Deurenberg BMI formula method.
Input Data
Results
Fat mass vs lean body mass
Body fat % trend by weight
Chart notes:The pie chart shows the proportion of fat mass versus lean mass in body weight; the line chart shows how body-fat percentage changes with weight at a fixed height.
At a glance:Enter height, weight, age, and circumferences to estimate body-fat percentage using the US Navy circumference method or the Deurenberg BMI formula method.
Formula
US Navy (M): %BF ≈ 495/(1.0324 − 0.19077·log10(waist−neck) + 0.15456·log10(height)) − 450.
US Navy (F): replace waist−neck with waist+hip−neck.
Deurenberg: %BF = 1.20·BMI + 0.23·age − 10.8·(sex) − 5.4 (sex: M=1, F=0).
$$\text{BF}_{\text{navy, male}} = \frac{495}{1.0324 - 0.19077\,\log_{10}(W-N) + 0.15456\,\log_{10}(H)} - 450$$How to Use
- Select sex and the estimation method.
- Enter height, weight, and (for BMI method) age; for the Navy method enter neck, waist, and hip (hip for females).
- The calculator returns body-fat %, fat mass, lean mass, and class.
FAQ
How does body-fat percentage differ from BMI?
BMI uses only height and weight and cannot tell muscle from fat; body-fat percentage directly measures the fat proportion. Two people with the same BMI can have very different body fat, so body fat reflects fat-loss progress better.
Which estimation method is more accurate?
The US Navy circumference method has an error of about ±3% for typical adults and is more accurate than the BMI formula; the BMI method is convenient but affected by ethnicity and age. The most accurate measurement remains professional instruments such as DEXA.
At what waist circumference is there a health risk?
The Hong Kong Department of Health advises adult men to keep waist below 90 cm (~36 in) and women below 80 cm (~32 in); exceeding this is central obesity and raises cardiovascular risk.
Why is an athlete's body-fat percentage lower?
Muscle is denser than fat; regular training raises muscle and lowers fat. But too low a body-fat percentage (men <5%, women <12%) disrupts hormones and health, so chasing extremely low values is not advisable.
Related Tools
References
Content review: Calculatorism Science Team. Results are for reference only; please refer to the relevant authorities for the official figures.