Body Fat Calculator

Validation studies typically find a standard error of about 3 to 4 percentage points against DEXA or hydrostatic weighing, with larger errors at the extremes of body composition. That is good enough to track a trend over months, but it is not precise enough to argue about a single point. Measure at the same time of day, with the same tape and the same tension, if you want the comparisons to mean anything.

For men, body fat % = 495 ÷ (1.0324 − 0.19077 × log₁₀(waist − neck) + 0.15456 × log₁₀(height)) − 450, with all measurements in centimetres. For women it is 495 ÷ (1.29579 − 0.35004 × log₁₀(waist + hip − neck) + 0.22100 × log₁₀(height)) − 450.

The American Council on Exercise puts the fitness range at 14 to 17 percent for men and 21 to 24 percent for women, with 18 to 24 percent and 25 to 31 percent respectively counted as average. Essential fat — the minimum needed for normal function — is around 2 to 5 percent for men and 10 to 13 percent for women.

Measure the neck just below the larynx, sloping slightly downward at the front. Men measure the waist horizontally at the navel; women measure at the narrowest point of the torso. Keep the tape snug but not compressing the skin, and measure after breathing out normally.

For assessing body composition, yes — BMI cannot tell muscle from fat, so it misclassifies muscular people as overweight. But BMI is measured far more reliably, whereas a tape measure introduces its own error. They answer different questions and are best read together.

No. The formula runs in JavaScript in your browser and nothing you enter is transmitted or stored. You can even use the tool with your network disconnected.