Body Fat Calculator — U.S. Navy & Skinfold Methods
Estimate your body fat percentage with a tape measure (U.S. Navy method) or skinfold calipers (Jackson-Pollock 3-site), compare it with a BMI-based estimate, and see your fat mass, lean mass and body-fat category.
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Body fat % × weight
Everything that isn't fat
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Deurenberg formula (BMI, age, sex)
Body Fat Categories (American Council on Exercise)
General reference ranges for adults. Healthy ranges also rise somewhat with age.
| Category | Men | Women |
|---|
How this calculator works
The U.S. Navy method estimates body fat from circumference measurements using a logarithmic formula, and is a widely used field method that doesn't require calipers or special equipment.
- Navy — men (cm): 495 ÷ (1.0324 − 0.19077 × log₁₀(waist − neck) + 0.15456 × log₁₀(height)) − 450
- Navy — women (cm): 495 ÷ (1.29579 − 0.35004 × log₁₀(waist + hip − neck) + 0.22100 × log₁₀(height)) − 450
- Jackson-Pollock 3-site: body density from the sum of three skinfolds and age (men: chest, abdomen, thigh; women: triceps, suprailiac, thigh), converted to body fat with the Siri equation: 495 ÷ density − 450.
- Deurenberg (BMI-based): 1.20 × BMI + 0.23 × age − 10.8 × sex (1 = male, 0 = female) − 5.4. A rough population estimate, shown for comparison only.
By Suhaib Hassan · Reviewed 28 September 2026 against the original published equations · How CalculatePilot verifies formulas →
How to make repeat measurements more useful
- Use the same measurement method and locations each time.
- Measure under similar conditions, such as a similar time of day.
- Keep the tape snug without compressing the skin.
- Repeat measurements when practical and look at the trend rather than one isolated percentage.
Consistent technique makes changes over time easier to interpret, even though the absolute percentage remains an estimate.
Accuracy of this method
The Navy method can be useful for consistent at-home tracking, but the size and direction of its error vary between people and it should not be presented as interchangeable with DEXA. Skinfold results also depend heavily on measurement technique and operator skill.
Comparing measurement methods
Besides the Navy circumference and skinfold methods used here, other common body fat estimation methods include bioelectrical impedance scales and DEXA scans. DEXA is generally considered the most accurate but requires specialized equipment, while circumference and caliper methods offer a reasonable free or low-cost alternative.
For tracking progress over time, consistency in measurement method and technique matters more than absolute accuracy — comparing this month's Navy method result to last month's using the same technique is more meaningful than comparing to a one-time DEXA scan result.
A worked example
A man with a 90 cm waist, 38 cm neck, and 178 cm height: using the Navy formula, this works out to about 20% body fat, in the "average" ACE category.
If his waist measured 100 cm instead (all else equal), the estimate rises to about 27% — illustrating how sensitive this method is to waist measurement specifically, making consistent, careful measurement technique important for tracking change over time.
Once you have a body fat estimate, our Lean Body Mass Calculator and the lean-mass formulas in the TDEE Calculator can use it. Medical information, not medical advice.
Sources
- U.S. Navy Body Composition Assessment guidance
- Hodgdon JA, Beckett MB. Prediction of percent body fat for U.S. Navy men and women from body circumferences and height. Naval Health Research Center, 1984.
- Jackson AS, Pollock ML. Generalized equations for predicting body density of men. Br J Nutr 1978;40:497–504. Jackson AS, Pollock ML, Ward A. Generalized equations for predicting body density of women. Med Sci Sports Exerc 1980;12:175–181.
- Deurenberg P, Weststrate JA, Seidell JC. Body mass index as a measure of body fatness. Br J Nutr 1991;65:105–114.
- American Council on Exercise — body fat percentage categories.
Read the guide: Healthy body fat percentage by age and sex
Body fat categories at a glance (ACE)
| 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% and above | 32% and above |
Essential fat is the minimum the body needs to function, not a target to aim for.
Worked examples with each method
| Method and inputs | Result | Category |
|---|---|---|
| Navy, man: waist 90 cm, neck 38 cm, height 178 cm | 20.1% | Average |
| Same man with a 100 cm waist | 26.7% | Obese |
| Same man with an 85 cm waist | 16.4% | Fitness |
| Navy, woman: waist 78 cm, hips 100 cm, neck 32 cm, height 165 cm | 31.4% | Average |
| Jackson-Pollock, man aged 30: chest + abdomen + thigh = 60 mm | 17.9% (density 1.0578) | Fitness |
| Jackson-Pollock, woman aged 30: triceps + suprailiac + thigh = 60 mm | 24.1% (density 1.0440) | Fitness |
| BMI-based (Deurenberg), man aged 30, 178 cm, 80 kg (BMI 25.2) | 21.0% | Average |
Five centimetres on the waist moves the Navy estimate by about four percentage points, which is why careful, repeatable measuring matters more than any single number.
Fat mass, lean mass and target weight
Fat mass = weight × body fat %. Lean mass = weight − fat mass. To see what you would weigh at a lower percentage while keeping the same lean mass, divide lean mass by (1 − target %). Example for an 80 kg person at 25%: fat mass 20 kg, lean mass 60 kg.
| Target body fat | Weight with the same 60 kg lean mass |
|---|---|
| 25% (now) | 80.0 kg |
| 20% | 75.0 kg |
| 15% | 70.6 kg |
| 12% | 68.2 kg |
This is a simple estimate. In practice some lean mass is usually lost along with fat, so recalculate as you go and treat the results as a guide, not a goal for any individual.
Which method should you use?
| Method | What you need | Main limitation |
|---|---|---|
| U.S. Navy | Tape measure: neck, waist, height, and hips for women | Very sensitive to the waist measurement; less reliable for very muscular people |
| Jackson-Pollock 3-site | Skinfold calipers and a second person | Depends on technique and operator skill |
| BMI-based (Deurenberg) | Height, weight, age, sex | A rough population estimate shown only for comparison |
Frequently asked questions
How accurate is the U.S. Navy body fat method?
It is a field estimate and measurement error can be meaningful. Accuracy varies with body composition, measurement technique and the method used; it should not be treated as equivalent to a clinical body-composition measurement.
Why does the formula differ for men and women?
Body fat distribution patterns differ by sex, so the formula includes hip measurement for women to account for typical fat distribution differences.
What is a healthy body fat percentage?
Reference ranges for body fat vary by age, sex, population and source. These categories are educational reference points, not personalized medical targets or diagnoses.
How often should I re-measure my body fat?
Monthly is a reasonable cadence for tracking meaningful change — body fat percentage doesn't shift dramatically week to week, so frequent measurement mostly captures measurement noise rather than real change.
How does the Navy method compare to a DEXA scan?
DEXA and circumference methods use different measurement approaches. A DEXA result should not be treated as a simple conversion or guaranteed ground truth for an individual; the Navy result is best used as a consistent field estimate.
Where exactly should I measure my waist and neck?
Waist is typically measured at the navel level, and neck just below the larynx — consistent placement each time you measure matters more than the exact spot, for tracking change over time.
Tape measure or skinfold calipers — which is better?
Both are estimates. Skinfolds taken by a trained person can be quite accurate, but results vary a lot with technique; the tape method is easier to repeat consistently at home. Pick one and use it the same way each time.
How do I calculate fat mass and lean mass from body fat percentage?
Fat mass is your weight multiplied by your body fat percentage, and lean mass is what remains. At 80 kg and 25%, fat mass is 20 kg and lean mass is 60 kg.
What would I weigh at a lower body fat percentage?
Divide your lean mass by (1 minus the target percentage). With 60 kg of lean mass, 20% body fat is 60 ÷ 0.80 = 75 kg. This assumes lean mass stays the same, which is rarely exactly true, so use it as a rough guide.
Is body fat percentage better than BMI?
They answer different questions. BMI only uses height and weight, so it cannot tell muscle from fat. Body fat percentage separates fat from lean mass, but its estimates have their own error, so many people track both.
Why do the Navy and skinfold methods give different results?
They measure different things: the Navy method infers fat from circumferences and height, while skinfolds estimate body density from fat folds under the skin. Each has its own error, so compare results from the same method over time.
Is the Navy method reliable for very muscular people?
It is less reliable. Waist and neck circumferences reflect muscle as well as fat, so the formula can misjudge people whose build differs from the population it was based on. Use it for tracking trends rather than as an exact figure.
Next Steps
Use your body-fat estimate in other calculators.