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- Body fat percentage is the share of your weight that is fat. The rest is lean mass: muscle, bone, organs and water.
- This calculator estimates it two ways: the U.S. Navy tape-measure method or a 3-site skinfold test with calipers.
- It also shows your fat mass, lean mass and the American Council on Exercise (ACE) category for your sex.
- Both methods are estimates for adults. This page is general information, not medical advice.
How to use the body fat calculator
Pick a method
Choose the tape measure (U.S. Navy) method if you only have a measuring tape, or skinfold calipers if you have them.
Choose sex and units
The formulas differ for men and women. Enter measurements in inches and pounds or in centimeters and kilograms.
Enter your measurements
For the tape method: height, neck and waist, plus hips for women. For calipers: three skinfolds in millimeters and your age.
Read your result
You get body fat percentage, fat mass, lean mass and your ACE category, with every step of the formula.
How to measure for the U.S. Navy method
Use a flexible tape, keep it snug but not tight, and measure on bare skin. Take each measurement twice and use the average.
Neck: just below the Adam’s apple, with the tape sloping slightly down at the front. Waist: men measure at the navel; women measure at the narrowest point of the waist. Hips (women): around the widest part of the buttocks. Height: without shoes.
How body fat percentage is calculated
U.S. Navy formulas (inches)
Men: body fat % = 86.010 × log10(waist − neck) − 70.041 × log10(height) + 36.76
Women: body fat % = 163.205 × log10(waist + hips − neck) − 97.684 × log10(height) − 78.387
Metric measurements are converted to inches first (centimeters ÷ 2.54).
Jackson-Pollock 3-site skinfold formulas
Men (chest, abdomen, thigh): density = 1.10938 − 0.0008267 × S + 0.0000016 × S² − 0.0002574 × age
Women (triceps, suprailiac, thigh): density = 1.0994921 − 0.0009929 × S + 0.0000023 × S² − 0.0001392 × age
Siri equation: body fat % = 495 ÷ density − 450
S is the sum of the three skinfolds in millimeters.
Body fat percentage chart
ACE body fat categories
From the American Council on Exercise.
- Essential fat Women 10–13% – Men 2–5%
- Athletes Women 14–20% – Men 6–13%
- Fitness Women 21–24% – Men 14–17%
- Average / acceptable Women 25–31% – Men 18–24%
- Obesity Women 32% or more – Men 25% or more
Women naturally carry more essential fat than men, which is why the ranges differ. The calculator rounds to the nearest whole percent to pick a category.
Worked examples
Example 1: a man, tape method
He is 70 in tall (5 ft 10 in), weighs 180 lb, with a 15 in neck and a 34 in waist.
- Formula 86.010 × log10(19) − 70.041 × log10(70) + 36.76
- Body fat 17.5%
- Fat mass 31.5 lb
- Lean mass 148.5 lb
- ACE category Acceptable
At 17.5% he sits just above the top of the fitness range for men.
Example 2: a woman, tape method
She is 64 in tall (5 ft 4 in), weighs 140 lb, with a 13 in neck, 30 in waist and 38 in hips.
- Formula 163.205 × log10(55) − 97.684 × log10(64) − 78.387
- Body fat 29.2%
- Fat mass 40.9 lb
- ACE category Average
The hip measurement is what makes the women’s formula different.
Example 3: a man, skinfold calipers
A 35-year-old man measures chest 12 mm, abdomen 22 mm and thigh 18 mm.
- Sum of skinfolds 52 mm
- Body fat (Siri) 16.2%
- ACE category Fitness
Skinfold results depend a lot on the skill of the person measuring.
How accurate is a body fat calculator?
Tape and caliper methods are practical estimates. Results are often a few percentage points away from a lab method such as a DEXA scan, and they can be further off for people with very high or very low body fat. Their real strength is tracking change: use the same method, the same person measuring, the same spots and the same time of day, and watch the trend over weeks rather than a single number.
Where a body fat calculator helps
Fitness progress
See whether weight changes come from fat or lean mass.
Beyond BMI
BMI cannot tell muscle from fat. Body fat percentage can.
Better BMR estimates
Use your body fat with the Katch-McArdle formula in the BMR calculator.
Goal setting
Set targets in body fat rather than weight alone.
Compare with your BMI, use your body fat in the BMR calculator for a Katch-McArdle estimate, see your FFMI, or plan meals with the protein intake calculator. This page is general information, not medical advice.
Body fat calculator FAQ
What is a healthy body fat percentage?
ACE lists 25–31% as average for women and 18–24% as acceptable for men, with lower ranges for fitness and athletes. Essential fat is about 10–13% for women and 2–5% for men.
How do I calculate body fat with a tape measure?
Measure your height, neck and waist, plus hips if you are a woman, and enter them in the U.S. Navy formula. The calculator does the log math for you.
Which is more accurate, tape or calipers?
Both are estimates. Calipers can be accurate in skilled hands, while the tape method is easier to repeat at home. Lab methods like DEXA are more precise.
Why is the formula different for women?
Women carry more essential fat and store more around the hips, so the women’s Navy formula adds a hip measurement and uses different constants.
How is body fat different from BMI?
BMI uses only height and weight, so it cannot tell fat from muscle. Body fat percentage estimates how much of your weight is actually fat.
How often should I measure body fat?
Every two to four weeks is enough. Daily changes are mostly water and measurement noise.