Body Fat Calculator
Estimate body fat percentage using the US Navy circumference method, with the fat mass and lean mass it implies.
Body fat percentage
16.9%
Fitness range for men
Fat mass
12.7 kg
Lean mass
62.3 kg
- Method
- US Navy circumference
- Waist − neck
- 47 cm
- Fat mass
- 12.7 kg
- Lean mass
- 62.3 kg
- Category
- Fitness
How this was calculated
- 1.Men: %BF = 495 / (1.0324 − 0.19077·log₁₀(waist − neck) + 0.15456·log₁₀(height)) − 450
- 2.Substituting: waist 85 cm, neck 38 cm, height 175 cm.
- 3.Result = 16.9% body fat.
- 4.Fat mass = 75 kg × 0.169 = 12.7 kg.
Tape measurements carry roughly ±3–4% error against a DEXA scan. Measure at the same time of day, relaxed, without compressing the tape.
How the body fat calculation works
The US Navy method estimates body fat from circumference ratios. Fat around the waist and neck changes the relationship between those measurements and total body fat, so the formula can infer a percentage without calipers.
For men, waist and neck are used; for women, hips are included because fat distribution differs. Measure the neck just below the larynx, the waist at the navel, and the hips at the widest point.
It is a practical field method, not a laboratory one. DEXA and hydrostatic weighing are more accurate but impractical for regular tracking — consistency of measurement matters more than absolute precision.
Worked example
A man, 175 cm, 75 kg, neck 38 cm, waist 85 cm.
- →waist − neck = 47
- →log₁₀(47) = 1.672, log₁₀(175) = 2.243
- →495 / (1.0324 − 0.319 + 0.347) − 450
Answer: About 19.4% body fat — the average range for men.
Body Fat FAQs
What is a healthy body fat percentage?
For men, roughly 8–20% is typical and healthy; for women, 21–33%, because women carry more essential fat. Athletic ranges are lower.
Why is the estimate different from my smart scale?
Scales use bioelectrical impedance, which is heavily affected by hydration. Neither method is exact; track one method consistently rather than comparing across devices.
Can I use inches?
The formula works with any consistent unit as long as height and circumferences use the same one, since the ratios are unitless. This tool takes centimetres for clarity.
Body Fat Calculator is part of the health calculators collection on Calcora, alongside 7 other tools. Results are calculated in your browser and are for information only — see our disclaimer.
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