What is my body fat?
Calculate your body fat percentage using various methods. Track your fitness progress and health metrics.
- Body fat
- 11.1%
Your estimated body fat is 11.1%, in the ACE Athletes range.
- ACE category
- Athletes
- Lean share
- 88.9%
- Fat mass
- 20 lb
- Lean body mass
- 160 lb
- BMI
- 25.8
Body fat: 11.1%. Your estimated body fat is 11.1%, in the ACE Athletes range.
How is my weight split?
This calculator gives general information only. It is not medical advice and does not replace a doctor or other health care provider. Talk with a professional about your results. Terms of use
How to calculate
Estimates body fat percentage with the U.S. Navy tape-measure equations or the Deurenberg BMI equation, with fat mass, lean mass, and the ACE category.
Example with the default inputs (Method U.S. Navy (tape measure), Sex Male, Age 30, Height 5 ft 10 in, Weight 180 lb, Waist 32 in, Neck 16 in): Your estimated body fat is 11.1%, in the ACE Athletes range.
Method: U.S. Navy (DoD), 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. BMI method (Deurenberg 1991): %BF = 1.20 × BMI + 0.23 × age − 10.8 × sex − 5.4 (sex 1 for men, 0 for women).
- The Navy equations take circumferences and height in inches; the calculator converts centimetres first (1 in = 2.54 cm).
- Categories are the American Council on Exercise (ACE) ranges, lower bound inclusive.
- The equations are for adults. They estimate body fat; lab methods such as DEXA measure it.
Worked examples
Each example is checked against the calculator on every build.
- Method U.S. Navy (tape measure), Sex Male, Age 30, Height 5 ft 10 in, Weight 180 lb, Waist 32 in, Neck 16 in gives Body fat 11.093848%, ACE category Athletes, Fat mass 20 lb.
- Method U.S. Navy (tape measure), Sex Female, Age 30, Height 5 ft 5 in, Weight 140 lb, Waist 30 in, Neck 13 in, Hip 40 in gives Body fat 31.087927%, ACE category Average.
- Method U.S. Navy (tape measure), Sex Male, Age 40, Height 5 ft 10.9 in, Weight 187.4 lb, Waist 35.43 in, Neck 15.75 in gives Body fat 18.462079%, ACE category Average, Lean body mass 152.8 lb.
- Method BMI method (Deurenberg), Sex Male, Age 30, Height 5 ft 10 in, Weight 180 lb gives Body fat 21.692455%, BMI 25.827046, ACE category Average.Source: Deurenberg et al. (1991): 1.20 × BMI 25.83 + 0.23 × 30 − 10.8 × 1 − 5.4 = 21.69%
- Method BMI method (Deurenberg), Sex Female, Age 45, Height 5 ft 3 in, Weight 141.1 lb gives Body fat 34.95%, ACE category Obese.Source: Deurenberg et al. (1991): BMI 64 ÷ 1.6² = 25
How body fat is worked out
Pick a method.
U.S. Navy (tape measure)
These are the Department of Defense circumference equations (Hodgdon and Beckett, 1984). Every length is in inches; the calculator converts centimetres first (1 in = 2.54 cm, exactly). log10 is the base-10 logarithm.
- 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
Men measure the waist at the navel; women at the narrowest point. The hip is used for women only. For men the waist must be larger than the neck, and for women waist plus hip must be larger than the neck, or the logarithm has no value. A result at or below 0% or at or above 100% means the measurements are outside the range the equation works for, and the calculator shows no answer.
BMI method (Deurenberg, 1991)
- BMI = weight in kg ÷ (height in m)²
- Body fat % = 1.20 × BMI + 0.23 × age − 10.8 × sex − 5.4, where sex is 1 for men and 0 for women.
This method does not use the tape measurements. As with the Navy method, a result at or below 0% or at or above 100% has no answer.
Fat mass and lean mass
- Fat mass = weight × body fat % ÷ 100
- Lean body mass = weight − fat mass
ACE categories
The category is read from these ranges; each lower bound is inclusive (a man at exactly 14.0% is in Fitness).
| Category | Men | Women |
|---|---|---|
| Below essential fat | under 2% | under 10% |
| Essential fat | 2% to under 6% | 10% to under 14% |
| Athletes | 6% to under 14% | 14% to under 21% |
| Fitness | 14% to under 18% | 21% to under 25% |
| Average | 18% to under 25% | 25% to under 32% |
| Obese | 25% or more | 32% or more |
Assumptions
- The equations are for adults and give an estimate, not a measurement.
- Values are not rounded between steps.
Worked examples by hand
Man, 5 ft 10 in, 180 lb, waist 32 in, neck 16 in (Navy). 86.010 × log10(32 − 16) − 70.041 × log10(70) + 36.76 = 86.010 × 1.20412 − 70.041 × 1.84510 + 36.76 = 103.566 − 129.233 + 36.76 = 11.09%, in the Athletes range. Fat mass = 81.647 kg × 0.11094 = 9.058 kg (about 20.0 lb).
Woman, 5 ft 5 in, waist 30 in, hip 40 in, neck 13 in (Navy). 163.205 × log10(30 + 40 − 13) − 97.684 × log10(65) − 78.387 = 163.205 × 1.75587 − 97.684 × 1.81291 − 78.387 = 286.566 − 177.092 − 78.387 = 31.09%, Average.
Man, 180 cm, 85 kg, waist 90 cm, neck 40 cm (Navy, metric tape). 90 − 40 = 50 cm = 19.685 in; 180 cm = 70.866 in. 86.010 × log10(19.685) − 70.041 × log10(70.866) + 36.76 = 86.010 × 1.29414 − 70.041 × 1.85044 + 36.76 = 18.46%, Average. Lean mass = 85 − 85 × 0.18462 = 69.31 kg.
Man, 30, 5 ft 10 in, 180 lb (BMI method). BMI = 81.647 ÷ 1.778² = 25.827. Body fat = 1.20 × 25.827 + 0.23 × 30 − 10.8 − 5.4 = 30.993 + 6.9 − 16.2 = 21.69%, Average.
Woman, 45, 1.60 m, 64 kg (BMI method). BMI = 64 ÷ 2.56 = 25. Body fat = 1.20 × 25 + 0.23 × 45 − 5.4 = 30 + 10.35 − 5.4 = 34.95%, Obese.
Other questions people ask
How does the body fat calculator work?
The calculator applies established formulas to estimate body fat. The U.S. Navy method uses log-based equations with waist, neck, and height for men, and waist, hip, neck, and height for women. The BMI method uses BMI, age, and sex (the Deurenberg formula). Both show fat mass (weight × body fat percent) and lean body mass (weight minus fat mass).
What is a healthy body fat percentage?
Healthy body fat ranges differ by sex. According to the American Council on Exercise (ACE): Essential fat: Men 2–5%, Women 10–13%; Athletes: Men 6–13%, Women 14–20%; Fitness: Men 14–17%, Women 21–24%; Average: Men 18–24%, Women 25–31%; Obese: Men ≥25%, Women ≥32%.
Why does body fat percentage matter?
Monitoring body fat is more meaningful than weight alone. Two people with the same weight can have very different body compositions. Body fat percentage directly reflects how much fat you carry, helping you track fat loss versus muscle gain. Excess fat, especially visceral fat, is linked to higher risk of heart disease, diabetes, and other conditions.
How accurate is this calculator?
This calculator provides an estimate based on population averages. For clinical precision, lab methods like DEXA or hydrostatic weighing are better. For home use, this calculator is convenient and consistent for tracking trends over time.
How do I measure correctly?
Height: Stand straight without shoes. Weight: Use a reliable scale. Waist: men measure at the navel while relaxed; women measure at the narrowest point of the waist. Neck: Measure just below the Adam's apple. Hip (women): Measure around the widest part of the hips. Use a non-stretch tape on bare skin. Don't squeeze the tape too tightly or hold your breath. Measure first thing in the morning for consistency.
What is Lean Body Mass?
Lean Body Mass (LBM) is everything except fat: muscle, organs, bone, water, etc. Our calculator shows LBM in pounds or kg. Maintaining LBM is important for metabolism and strength.
How often should I check my body fat?
It's best to check monthly rather than daily to see real changes. Always measure under similar conditions (e.g. morning, before meals).
Can I use this calculator at any age?
The formulas are generally for adults. For children, teens, or older adults, consult a professional. Norms are mostly based on younger adults.
Is low body fat always better?
No. Essential fat is needed for hormone and organ function. Excessively low body fat can be unhealthy. Always interpret your number along with how you feel and under medical guidance.