Case 1
- Sex
- Male
- Height
- 178cm
- Neck circumference
- 37cm
- Waist circumference
- 86cm
18.0%
Open with these valuesBody Fat Percentage Calculator
Change any value to update the result.
17.2%
Body fat (US Navy method): 17.2 %- In other units
- 70.1 in · 15.0 in · 33.9 in
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Examples
The US Navy method estimates body fat from a few tape measurements instead of calipers. It is repeatable and free, but it reads shape rather than tissue, so it can be several percentage points off for very lean or very muscular people.
The numbers at a glance
Held fixed: Sex Male, Height 178.0 cm, Neck circumference 38.0 cm.
| Waist circumference (cm) | Body fat (US Navy method) (%) |
|---|---|
| 70.0 | 2.8 |
| 80.0 | 12.4 |
| 86.0Your value | 17.2 |
| 90.0 | 20.1 |
| 100.0 | 26.7 |
| 110.0 | 32.5 |
| 120.0 | 37.6 |
Worked examples
Case 2
- Sex
- Female
- Height
- 165cm
- Neck circumference
- 33cm
- Waist circumference
- 70cm
- Hip circumference (women)
- 95cm
24.3%
Open with these valuesCase 3
- Sex
- Male
- Height
- 185cm
- Neck circumference
- 38cm
- Waist circumference
- 78cm
9.5%
Open with these valuesHow it's calculated
US Navy: % = 495 / (a − b·log₁₀(girth) + c·log₁₀(cm)) − 450
- StepMeasure your neck just below the larynx, tape sloping slightly down at the front.Neck circumference=38cm
- StepMeasure your waist at the navel for men, at the narrowest point for women.Waist circumference=86cm
- StepWomen also measure the hips at the widest point.
- ResultEnter the measurements and read the estimated percentage.17.2%
What this number means
Body fat percentage is the share of your total weight that is fat tissue, and unlike BMI it separates fat from muscle. This calculator uses the US Navy circumference method, developed by Hodgdon and Beckett at the Naval Health Research Center in 1984. It estimates body density from a handful of tape-measure readings — neck, waist, height, and for women the hips — and converts that density into a percentage.
The constants come from a regression against personnel whose body fat was measured by underwater weighing, which is why they look arbitrary: they are fitted numbers, not physical quantities. Read the result against the American Council on Exercise reference ranges, where the fitness band sits at roughly 14 to 18 percent for men and 21 to 25 percent for women. Those are population benchmarks, not disease thresholds.
Below the fitness band lies essential fat, the minimum needed for hormone regulation and organ protection, and dropping under it is dangerous rather than impressive. The caveat that matters most is precision. The method carries a typical error of three to four percentage points against a DEXA scan, and your own measuring adds to that: a single centimetre off at the waist moves the answer by half a point to a full point. Measure twice, take the average, and use the number to track a direction over months rather than to settle a question today.
Tape placement decides the result
The method reads circumferences, so a centimetre of drift at the waist moves the percentage. Measure relaxed, at the same landmarks, every time.
Hip is read for women only
The male equation uses neck and waist alone. The hip field stays visible so the input column does not jump when you switch.
Use it for the trend
Circumference methods carry a few percentage points of spread against a scan. The direction over several weeks is more trustworthy than any single reading.
Commonly misread
MisconceptionThis is as accurate as a DEXA scan.
CorrectionIt is a regression on circumferences, fitted to a military population. Read it as an estimate with a few points of spread either way.
MisconceptionLower body fat is always better.
CorrectionEssential fat has a floor, and that floor is higher for women than for men. Below it the number stops being a fitness measure.
Questions
How accurate is the Navy method?
It reads shape, not tissue, so it is repeatable but not precise. For very lean or very muscular people it can sit several percentage points away from a laboratory measurement — useful for tracking a direction over months, not for a single verdict.
Where do I measure the waist?
At the narrowest point for women and at the navel for men, with the tape level and the skin not compressed. The measurement dominates the result: at 178 cm and a 38 cm neck, moving the waist from 86 to 96 cm takes the estimate from 17.2 % to 24.2 %.
Why do women need a hip measurement?
The equation for women uses waist plus hip minus neck, the one for men only waist minus neck. With the same 178 cm, 38 cm neck and 86 cm waist, the calculator returns 17.2 % for a man and 26.6 % for a woman.
Can I enter inches?
Select in above the form and enter every measurement directly in inches. Select cm for centimetres. The calculator converts units for you; do not convert the values first.
How is this different from BMI?
BMI uses only weight and height and cannot separate muscle from fat. This method measures where the body is thick and where it is thin, which is why two people with the same BMI can land far apart here.