BMI Calculator
Work out BMI from height and weight, in metric or imperial units.
Health Calculators
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Body Fat Calculator
Estimate body fat from tape measurements.
Body Fat Calculator tool
The formula differs because fat distribution does.
Measured just below the larynx.
At the navel for men, at the narrowest point for women.
Women only: at the widest point.
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Body fat
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Category
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Fat mass
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Lean mass
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BMI for comparison
| Category | Men | Women |
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A tape estimate carries an error of several percentage points against a DEXA scan. It is useful for tracking a change in yourself over time, where the error is consistent, and much less useful for comparing yourself with somebody else.
About the Body Fat Calculator
Body Fat Calculator uses the US Navy circumference method, which estimates body fat from a few tape measurements rather than from weight alone. For men it needs height, neck and waist; for women it also needs the hip measurement, because fat distribution differs.
Its advantage over BMI is that it distinguishes fat from everything else. A muscular person can have a BMI in the overweight range and a body fat percentage in the athletic one, and the two numbers shown together make that visible. Fat mass and lean mass in kilograms are more useful still, because they are what actually changes when training or diet changes.
The accuracy is worth being blunt about: against a DEXA scan the tape method is typically within three or four percentage points, and it can be further out for people at the extremes. That makes it good for tracking your own trend, where the error is consistent from week to week, and poor for comparing yourself with somebody else measured a different way.
This is general information and not medical advice. The formula cannot know your medical history, your medication, your body composition or anything else specific to you. Speak to a doctor or another qualified professional about any question concerning your health, and never delay seeking advice because of a figure on this page.
Your measurements are processed inside your own browser. Height, weight, age and anything else you enter never leave your device, nothing is logged, and nothing survives closing the tab.
How to use the Body Fat Calculator
- Choose sexThe fields below change to match what you pick, so only the figures that matter to your case are asked for.
- Enter height (cm), weight (kg) and neck (cm)Decimals are fine, and thousands separators are accepted and ignored.
- Read the body fat, category and fat massThe figures update as you type. The Calculate button is there if you would rather press something, but nothing waits for it.
- Copy or check the resultCopy the summary with the copy button, or open the table to check it row by row.
Features
- Shows body fat, category, fat mass, lean mass and bmi for comparison together, so you are not running it twice
- A results table you can read across
- Updates as you type, with no button to press and no page reload
- Copy the result in one click
- Free, no sign-up, and it runs entirely in your browser
Who uses this tool
The body fat calculator is used by writers, developers, students, marketers and anyone else who needs the job done once without installing software. Common cases include:
- Tracking body composition change over months
- Getting a figure BMI cannot give for a muscular build
- Estimating lean mass for a Katch-McArdle BMR
- Checking progress without access to a scan
Frequently asked questions
How accurate is the tape method?
Usually within three to four percentage points of a DEXA scan, and consistently wrong in the same direction for the same person, which is why it tracks change well.
Where exactly do I measure?
Neck just below the larynx, sloping slightly downward at the front. Waist at the navel for men, at the narrowest point for women. Hips at the widest point. Keep the tape level and snug, not tight.
What is a healthy body fat percentage?
The table shows the common ranges, which differ substantially between men and women. Essential fat is the minimum the body needs; below it is not a goal.
Related tools
If the body fat calculator is not quite what you need, these other free tools solve closely related problems, and there are 19 more in health calculators.
Lean Body Mass Calculator
Lean body mass by three published formulas.
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Waist to Hip Ratio Calculator
Waist to hip ratio with the WHO risk categories.
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Ideal Weight Calculator
Ideal weight by four formulas, plus the healthy BMI range.
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BMR Calculator
Basal metabolic rate by three published equations.
Health Calculators
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Checked and rebuilt on 2026-10-14. The method this calculator uses is described in the section above, and corrections go through the contact page.