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📐 Body Fat Calculator

Estimate your body fat percentage using the US Navy circumference method.

Enter Your Values

Your height in cm
Measure around base of neck
Measure at navel level
Measure at the widest point (leave empty for men)

How Body Fat Percentage Is Estimated — and What It Means

This calculator uses the US Navy circumference method, one of the most practical field-based estimation techniques. It uses neck, waist, and (for women) hip circumference measurements along with height to estimate body fat percentage. The formula was developed and validated by the US Navy in the 1980s and is widely used in military, fitness, and clinical settings because it requires only a measuring tape — no specialised equipment needed.

The accuracy of circumference-based methods is moderate: typically within 3–5% of more precise measures like DEXA (Dual-Energy X-ray Absorptiometry) scans, which are considered the gold standard. Underwater weighing (hydrostatic testing) and air displacement plethysmography (Bod Pod) are also highly accurate. Bioelectrical impedance (found in many smart scales) varies widely in accuracy depending on hydration levels, time of day, and the quality of the device. For tracking change over time, any method is useful as long as you use the same method consistently.

How to measure accurately: neck circumference — measure at the midpoint of the neck, below the larynx, perpendicular to the long axis. Waist circumference (for the Navy formula) — measure at the navel, not at the narrowest point. Hip circumference (women only) — measure at the widest point across the buttocks. Take each measurement twice and use the average. Measure in the morning before eating, in a relaxed standing posture.

What do the numbers mean? For men, essential fat (the minimum needed for bodily function) is 2–5%. Athletes typically carry 6–13%. Fitness-oriented individuals 14–17%. "Average" is 18–24%, and above 25% is generally considered overweight for health purposes. For women, essential fat is higher at 10–13%, with athletes at 14–20%, fitness at 21–24%, average at 25–31%, and above 32% considered overweight. These categories are general guidelines — individual health context matters.

Body fat percentage is a more meaningful health metric than body weight alone. Two people at the same weight can have very different body fat percentages and health risk profiles, depending on their muscle mass, bone density, and fat distribution. Waist circumference is also independently predictive of cardiovascular risk, regardless of total body fat.

How to Measure and Interpret Body Fat Percentage

Body fat percentage is the proportion of your total body weight that is fat mass, as opposed to lean mass (muscle, bone, organs, water). Unlike BMI, it distinguishes between fat and muscle, making it a more meaningful health indicator for active individuals.

Healthy body fat ranges differ by sex: for men, 10-20% is generally considered fit, 20-25% acceptable, above 25% is excess. For women, 18-28% is fit, 28-33% acceptable, above 33% is excess. Athletes often sit below these ranges.

Frequently Asked Questions

What is the most accurate way to measure body fat? +
DEXA scan is the gold standard, accurate to within 1-2% but requires a medical facility. Hydrostatic weighing and Bod Pod (air displacement) are also highly accurate. Skinfold calipers done by a trained professional are reasonably accurate. The US Navy method used here is practical and repeatable, within 3-4% for most people.
Can you have a normal BMI but high body fat? +
Yes — this is called normal-weight obesity or skinny-fat. A person can have a BMI in the healthy range while carrying excess fat relative to muscle. This is common in sedentary people who have lost muscle mass with age. Body fat percentage reveals this; BMI does not.
Does body fat percentage change with age? +
Yes. Average body fat tends to increase with age even without weight gain, because muscle mass naturally declines (sarcopenia) from around age 30 unless actively maintained through resistance training. This is why activity level is important when interpreting body fat readings.