Body fat calculator
Estimate your body fat percentage three ways: the U.S. Navy tape method, a 3-site skinfold test, or a BMI-based estimate. Add your weight to get fat mass, lean mass and a goal weight.
Hodgdon & Beckett (1984) circumference equations, used by the U.S. Navy.
Enter height, neck and waist to see your estimate.
What moves the number: the waist
The Navy formula uses the logarithm of waist minus neck. Neck barely changes as you lean out, so the waist carries the estimate. Drag to see what a smaller (or bigger) waist would do to your result.
The Navy body fat formula
Developed by Hodgdon and Beckett at the Naval Health Research Center (1984) and still used for U.S. military body-composition standards, with measurements in inches:
- Men: %BF = 86.010 × log₁₀(waist − neck) − 70.041 × log₁₀(height) + 36.76
- Women: %BF = 163.205 × log₁₀(waist + hip − neck) − 97.684 × log₁₀(height) − 78.387
The other two methods
- Jackson-Pollock 3-site skinfold: body density = 1.10938 − 0.0008267·S + 0.0000016·S² − 0.0002574·age (men, chest + abdomen + thigh) or 1.0994921 − 0.0009929·S + 0.0000023·S² − 0.0001392·age (women, triceps + suprailiac + thigh), where S is the sum in mm. Body fat % = 495 ÷ density − 450 (Siri, 1961).
- BMI-based (Deurenberg 1991): %BF = 1.2 × BMI + 0.23 × age − 10.8 × sex − 5.4, with sex = 1 for men and 0 for women.
Whichever you pick, stick with it: switching methods mid-diet makes the trend meaningless. See the body fat percentage chart for healthy ranges by age, or the Army body fat calculator for the military one-site tape test.
This calculator converts centimetres for you. For the best tracking, measure on the same morning each check-in and log it in the measurement tracker; this page then pre-fills itself. To turn the result into muscle numbers, try the FFMI calculator or lean body mass calculator.
ACE body fat categories
| Category | Men | Women |
|---|---|---|
| Essential fat | 2–5% | 10–13% |
| Athletes | 6–13% | 14–20% |
| Fitness | 14–17% | 21–24% |
| Average | 18–24% | 25–31% |
| Obese | 25%+ | 32%+ |
Questions people ask
How accurate is the Navy body fat calculator?
The U.S. Navy circumference method (Hodgdon & Beckett, Naval Health Research Center, 1984) typically lands within about 3–4 percentage points of hydrostatic weighing for most people. It is less accurate for very lean or very muscular builds and for people who carry fat unusually. Its real strength is tracking change: measured the same way each time, the trend is reliable.
Where do I measure for the Navy method?
Neck just below the larynx (Adam’s apple), tape angled slightly down at the front. Men measure the waist horizontally at the navel; women at the narrowest point of the waist, plus hips at the widest point of the buttocks. Stand relaxed and don’t suck in.
What is a healthy body fat percentage?
The American Council on Exercise (ACE) chart puts “fitness” at 14–17% for men and 21–24% for women, and “average” at 18–24% for men and 25–31% for women. Essential fat is about 2–5% for men and 10–13% for women; going near those levels is not healthy long term.
Why does my body fat estimate barely change when I lose weight?
The formula is driven by waist minus neck. If most early loss is water, the waist moves little. As fat comes off your midsection, the estimate drops. Around 2.5 cm (1 in) off the waist typically lowers the estimate by roughly 1.5–2.5 points.
Which body fat method should I use?
Use the Navy tape method if you have a tape measure: it needs no equipment and tracks change well. Use the 3-site skinfold method if you own calipers and can pinch consistently. The BMI-based estimate (Deurenberg, 1991) needs only height, weight and age, but it cannot tell muscle from fat, so it overestimates lean, muscular people and is the least useful for tracking a cut or recomp.
How do I calculate my goal weight for a target body fat?
Keep your lean mass constant and solve for total weight: goal weight = lean mass ÷ (1 − target body fat). Example: 80 kg at 25% is 60 kg lean; at 18% that is 60 ÷ 0.82 = 73.2 kg. Real diets lose a little lean mass too, so treat the result as a floor-to-aim-for, not a promise.
Where are the Jackson-Pollock 3 skinfold sites?
Men: chest (diagonal fold halfway between armpit and nipple), abdomen (vertical fold 2 cm right of the navel) and thigh (vertical fold midway between hip crease and kneecap). Women: triceps (vertical, back of the upper arm), suprailiac (diagonal, just above the hip bone) and thigh. Pinch on the right side, read the caliper after about two seconds, and average two readings per site.
Is the Army body fat calculator the same as the Navy one?
No. Since Army Directive 2023-11 the Army uses a one-site equation (weight plus abdomen at the navel). The Navy formula on this page uses height, neck and waist. They are different regressions and give different numbers; use the Army body fat calculator for that standard.