Body Fat Calculator (US Navy Method)
Estimate your body fat percentage from height, neck, waist and hip measurements using the US Navy tape-measure method
Last updated: November 2, 2026
US Navy body fat formulas
Measurements are in inches (centimeters are converted by dividing by 2.54).
Men: body fat % = 86.010 × log₁₀(waist − neck) − 70.041 × log₁₀(height) + 36.76
Women: body fat % = 163.205 × log₁₀(waist + hip − neck) − 97.684 × log₁₀(height) − 78.387
Fat mass and lean mass
Fat mass = Body weight × Body fat % ÷ 100
Lean mass = Body weight − Fat mass
How to measure
- Height: barefoot, standing straight.
- Neck: just below the larynx, with the tape sloping slightly downwards at the front.
- Waist: for men, across the navel; for women, at the narrowest point of the waist.
- Hip (women only): around the widest part of the hips and buttocks.
Keep the tape snug but not tight and measure two or three times, taking the average.
Body fat categories
These are the American Council on Exercise (ACE) ranges:
| Category | Men | Women | |---|---|---| | Essential fat | 2 to 5% | 10 to 13% | | Athletes | 6 to 13% | 14 to 20% | | Fitness | 14 to 17% | 21 to 24% | | Average | 18 to 24% | 25 to 31% | | Obese | 25% and over | 32% and over |
Some body fat is essential for health, so a lower number is not always better.
How to estimate your body fat percentage
- Choose your units and your sex.
- Take your measurements with a flexible tape measure as described under each field. Measure after waking up, before eating, for consistent results.
- Enter your height, neck and waist (and hip, for women).
- Add your body weight (optional) to see how many kilograms or pounds of fat and lean mass that body fat percentage represents.
- Read the results. You will get your estimated body fat percentage and where it falls in the ACE categories.
Re-measure every few weeks under the same conditions to follow your trend. A single measurement is an estimate, so the change over time is more useful than any one number.
Frequently Asked Questions
How do you calculate body fat percentage with a tape measure?
The US Navy method uses your height, neck and waist (plus hip for women) in a logarithmic formula. For men it is 86.010 × log10(waist − neck) − 70.041 × log10(height) + 36.76, with measurements in inches. A man 178 cm tall with a 38 cm neck and 85 cm waist comes out at about 16.5%.
How accurate is the US Navy body fat calculator?
It is an estimate and is typically within a few percentage points of more precise methods such as DEXA scans, though it can be less accurate for very muscular or very lean or very heavy people. It is best for tracking changes over time using consistent measurements.
What is a healthy body fat percentage?
By the ACE categories, men are generally in the "fitness" to "average" range at about 14 to 24% and women at about 21 to 31%. Women naturally carry more essential body fat than men. Healthy ranges also change with age, so talk to a health professional about your own target.
Why do women enter a hip measurement?
Women store more fat around the hips and thighs, so the formula for women uses waist, hip and neck together. Men do not use the hip measurement.
Is body fat percentage better than BMI?
They measure different things. BMI only uses height and weight, so it cannot tell muscle from fat, and a muscular person can have a high BMI with low body fat. Body fat percentage describes body composition more directly. Many people use both along with waist measurements.
What is lean body mass?
It is everything in your body that is not fat: muscle, bone, organs and water. Subtract your fat mass from your total weight to get it. The FFMI calculator can turn lean mass into a muscularity index.
How can I lower my body fat percentage?
A modest calorie deficit, enough protein, strength training and consistent sleep are the common recommendations. Aim for gradual change over weeks and months rather than quick fixes, and see a doctor or dietitian before making big changes.
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