Body Fat Calculator
It estimates body fat percentage and lean mass from tape measurements using the US Navy circumference method.
Body fat
18.4%
Fat mass
32.4 lb
Lean mass
143.6 lb
Category
Average
What it calculates
It estimates body fat percentage and lean mass from tape measurements using the US Navy circumference method.
Why it matters
Body composition tracks health and training progress far better than scale weight alone.
Who it's for
Lifters, athletes, and anyone whose weight is stable while their shape changes.
Formula
- Neck
- Neck circumference
- Waist
- Waist at the navel
- Hip
- Hip circumference (women)
Worked example
Male, 180 cm, waist 88 cm, neck 39 cm
- 1BF% = 495 / (1.0324 − 0.19077·log₁₀(waist − neck) + 0.15456·log₁₀(height)) − 450
- 2= 495 / (1.0324 − 0.19077·log₁₀(49) + 0.15456·log₁₀(180)) − 450
≈ 17.6% body fat — the fitness range for men
How the body fat calculator works
The Navy method uses log-transformed circumference ratios calibrated against hydrostatic weighing. Women include hip circumference because fat distribution differs.
The US Navy circumference method estimates body fat from tape measurements. Measure the neck below the larynx, the waist at the navel, and (for women) the hips at the widest point.
It is an estimate within roughly ±3% of a DEXA scan for most people — useful for tracking a trend rather than as a clinical figure.
Common mistakes
- Pulling the tape tight — it should sit flat without compressing.
- Measuring at different times of day or after eating.
- Expecting DEXA-level precision from a tape measure.
Tips and best practice
- Measure first thing in the morning, in the same conditions, once a fortnight.
- Track the direction of change rather than the absolute number.
Frequently asked questions
How accurate is the US Navy body fat method?
Typically within about 3–4 percentage points of hydrostatic weighing for most people.
What is a healthy body fat percentage?
Roughly 10–20% for men and 18–28% for women, with athletes usually lower.
Why do women need a hip measurement?
Female fat distribution weights the hips more, so the formula is calibrated differently.
How accurate is the Navy tape method?
Within roughly ±3% of a DEXA scan for most people. It is far better at tracking change over time than at producing a single definitive number.
Where exactly do I measure?
Neck just below the larynx, waist at the navel for men and at the narrowest point for women, and hips at the widest point. Keep the tape level and snug without compressing.
Why do men and women use different formulas?
Fat distribution differs, so the female equation includes hip circumference and uses different coefficients. Using the male formula on a woman badly understates the result.
Related calculators
Further reading
Methodology & trust
- Formula source
- US Navy circumference method (Hodgdon & Beckett).
- Last updated
- 2026-07-28
- Privacy
- Every calculation runs in your browser. No inputs are sent to a server or stored.
- Accessibility
- Keyboard navigable, labeled inputs and WCAG AA color contrast.