Body Fat Calculator
With height 70 inch, waist 34 inch, neck 15 inch, hips 0 inch and 1 more field, body fat comes to 17.5 % — body fat. It is reached in 3 steps, the last of which is max(17.513085 + -0, 0), and each one is printed on the page with its numbers filled in. The formula is the one published by US Navy Physical Readiness Program, not an approximation fitted to it.
Body fat percentage from tape measurements using the US Navy circumference method, plus lean mass.
Formula and sources checked · How we check
Sex at birth Male, Height 5' 10", Waist 34 inch, Neck 15 inch
17.5 %
Body fat for the example below. Editing a field recomputes the calculator below; this figure holds the answer the page was loaded with.
It is written into the HTML rather than drawn by a script, so a search engine reading this page without running JavaScript still finds an answer.
- Body fat
max(17.513085 + -0, 0)17.513 %- Fat mass
175 * 17.513085 / 10030.648 lbs- Lean body mass
175 - 30.647899144.352 lbs
Worked example
A 5'10" man with a 34 in waist and 15 in neck comes out at 17.5% body fat — 30.7 lb of fat and 144 lb of lean mass. The lean figure is the useful one to track: losing weight while it stays flat means the loss was fat.
How to work it out yourself
- 1.Measure at the narrowest point of the waist for women and at the navel for men, tape level and snug but not compressing.
- 2.Measure the neck just below the larynx with the tape sloping slightly downward at the front. The neck term is what takes frame size out of the estimate.
- 3.Take each measurement twice and average them. The formula is logarithmic, so a centimeter of tape error moves the answer by roughly half a percentage point.
The formula
- Body fat
max(17.513085 + -0, 0) - Fat mass
175 * 17.513085 / 100 - Lean body mass
175 - 30.647899
Source: US Navy Physical Readiness Program — body composition assessment, NIH — assessing body composition
Questions people actually ask
- How accurate is the tape method?
- Within about 3–4 percentage points of a DEXA scan for most people, and it errs most on the very lean and the very muscular. Its real strength is repeatability — measured the same way each month, the trend is reliable even when the absolute number is not.
- What counts as a healthy range?
- Roughly 10–20% for men and 18–28% for women, with athletes below and essential fat floors around 3% and 12% respectively. Age shifts the healthy band upward by a few points per decade.
- Why does only the waist really move?
- Neck and height barely change, so the equation is effectively tracking waist circumference. That is a feature: abdominal fat is the depot most tied to metabolic risk, which is why waist alone is a decent screening measure.
Related
- BMI CalculatorBody mass index from height and weight in either metric or US units, with the CDC category cut-offs.
- Ideal Weight CalculatorReference weight from height by four standard clinical formulas, and the BMI-healthy range they sit inside.
- BMR CalculatorBasal metabolic rate from the Mifflin-St Jeor, revised Harris-Benedict and Katch-McArdle equations at once, with the disagreement between them shown.
- Body Surface Area CalculatorBody surface area by the Mosteller and Du Bois formulas, the measure chemotherapy and paediatric doses are scaled by.
- Body Shape CalculatorBody shape from bust, waist and hips, with the waist-to-hip and waist-to-height ratios the WHO uses to judge risk.
- Army Body Fat CalculatorThe Army’s waist-to-height assessment that replaced the tape test in July 2026, with the waist measurement the 0.55 standard allows at your height.
Part of a job
- Losing weight — 6 pages, in the order the questions arrive
Put this calculator on your site
Free, no attribution required beyond the link.
<iframe src="https://rulecalculators.com/embed/body-fat" width="100%" height="420" style="border:1px solid #e7e4de;border-radius:12px" title="Body Fat Calculator"></iframe>