Body Fat Calculator guide
Body Fat Calculator: Estimate Your Body Fat Percentage
Use our body fat calculator to estimate your body fat percentage, fat mass and lean mass from your height, neck, waist and hip measurements using the US Navy method.
By the AllCalculator editorial teamUpdated 16 October 20262 min read
BMI tells you whether your weight is in a healthy range for your height, but it can't tell muscle from fat. A body fat percentage gets closer to what most people actually want to know. Our Body Fat Calculator estimates it with just a tape measure.
How to use the calculator (Body Fat Calculator)
- Choose your sex and units.
- Enter your weight and height.
- Measure your neck, waist and, for women, hips, and enter them.
You'll see your estimated body fat percentage, how much of your weight is fat and lean mass, and where you sit in common body fat ranges.
How to measure
- Neck: just below the Adam's apple, with the tape sloping slightly down at the front.
- Waist: men at the navel; women at the narrowest point.
- Hips: at the widest part of your bottom.
Measure on bare skin, standing relaxed, with the tape snug but not pressing in. Take each measurement twice and use the average.
The method
The calculator uses the US Navy circumference method, which links body fat to the difference between your waist (and hips) and your neck, adjusted for height. Studies find it's usually within 3 to 4 percentage points of more accurate methods such as DEXA scans.
Body fat ranges
| Category | Women | Men |
|---|---|---|
| Essential fat | 10–13% | 2–5% |
| Athletes | 14–20% | 6–13% |
| Fitness | 21–24% | 14–17% |
| Average | 25–31% | 18–24% |
| Above average | 32% or more | 25% or more |
These ranges come from the American Council on Exercise. Women naturally carry more essential fat than men.
A worked example
With the calculator's default settings, a woman who is 168cm tall and weighs 70kg, with a 34cm neck, 80cm waist and 98cm hips, has an estimated body fat of 29.6%. That's about 20.7kg of fat and 49.3kg of lean mass, in the average range.
Frequently asked questions
Is this as accurate as a body fat scale?
Home scales that use bioelectrical impedance can swing several percent depending on how hydrated you are. A tape measure is often just as reliable if you measure carefully and consistently.
What's a healthy body fat percentage?
There's no single figure, but the fitness and average ranges above are typical for healthy adults. Your waist size is a good simple check: the NHS suggests keeping it to less than half your height.
Why does my result change from week to week?
Small differences in where you measure make a big difference. Measure at the same time of day, in the same place, and look at the trend over several weeks.
For a quick check of your weight for your height, try our BMI Calculator or Lean Body Mass Calculator.
Sources and further reading
Links open official and independent websites in a new tab.
This guide is general information to help you understand your options. It isn't financial, tax, legal or building advice and doesn't take your personal circumstances into account. Figures were checked when the guide was last updated and can change, so confirm anything important with GOV.UK, HMRC, a regulated adviser or a qualified tradesperson.