Body Fat Calculator
Estimate body fat percentage.
Your details
For adults aged 18 and over. Results update as you type.
How to measure
- Use a flexible tape on bare skin, snug but not squeezing, and breathe out normally.
- Neck: just below the larynx (Adam's apple), tape level at the front.
- Waist: men, at the navel; women, at the narrowest point (usually just above the navel).
- Hip (women): around the widest part of the buttocks.
- Take each measurement two or three times and use the average.
Estimated body fat (US Navy method)
20.9%
AverageGeneral guide for men: average is 18–24%. Estimates like this can differ from a lab measurement by several percentage points.
Where you sit in the general guide (men)
General guide only. Healthy body fat varies with age and fitness.
Fat mass vs lean mass
Lean mass includes muscle, bone, organs and water.
Both methods side by side
| US Navy (measurements) | 20.9% |
| From BMI (Deurenberg) | 24.0% |
| Difference | 3.2 percentage points |
The BMI method cannot tell muscle from fat, so it tends to differ most for very muscular or very lean people.
How to Calculate Body Fat Percentage
This body fat calculator estimates your body fat percentage in two ways: from tape measurements using the US Navy method, or from your BMI, age and sex. It also shows your fat mass and lean mass and how your body fat level compares with a general guide for men or women. Use the measurement method if you have a tape measure to hand; use the BMI method for a quick figure when you do not.
Whichever body fat percentage calculator you use, treat the answer as an estimate. These methods are useful for tracking your own change over time, but they are not a diagnosis and can differ from a clinical measurement by several percentage points.
The Formulas
US Navy, women = 495 ÷ (1.29579 − 0.35004 × log₁₀(waist + hip − neck) + 0.22100 × log₁₀(height)) − 450
All measurements in centimetres. Imperial entries are converted first (1 inch = 2.54 cm).
Sex is 1 for men and 0 for women. Fat mass = weight × body fat %, and lean mass = weight − fat mass.
Worked Examples
Man, 35, 178 cm, 85 kg, neck 39 cm, waist 92 cm. The US Navy method gives 20.9% body fat, which is 17.7 kg of fat and 67.3 kg of lean mass. That sits in the average band for men (18–24%). His BMI is 26.8, and the BMI method gives 24.0%, about 3.2 percentage points higher than the measurement method.
Woman, 30, 165 cm, 62 kg, neck 33 cm, waist 72 cm, hip 98 cm. The US Navy method gives 26.9% body fat, or 16.7 kg of fat and 45.3 kg of lean mass, in the average band for women (25–31%). Her BMI is 22.8 (healthy weight), and the BMI method gives 28.8%, about 1.9 percentage points higher.
How to Measure
Stand relaxed and measure on bare skin with a flexible tape that is snug but not compressing. Measure the neck just below the larynx (Adam's apple). Men should measure the waist at the navel, while women should measure at the narrowest point, usually just above the navel. Women also measure the hips at the widest part of the buttocks. Breathe out normally, keep the tape level, and take each measurement two or three times. Small errors matter: because the formula uses the difference between waist and neck, a centimetre or two can shift the result by a percentage point or more.
Body Fat Categories (General Guide)
| Category | Women | Men |
|---|---|---|
| Below essential fat | Below 10% | Below 2% |
| Essential fat | 10–13% | 2–5% |
| Athletes | 14–20% | 6–13% |
| Fitness | 21–24% | 14–17% |
| Average | 25–31% | 18–24% |
| Above average | 32% and above | 25% and above |
This is a general guide based on commonly cited fitness ranges, not a clinical standard. Essential fat is the minimum the body needs to function, not a target, and what is healthy for you depends on your age, activity and health.
Accuracy and Other Ways to Measure
Tape-measure and BMI-based estimates are convenient, but they are indirect and can differ by several percentage points from other methods. DEXA scans and bioimpedance scales measure more directly, though each has its own limits, such as hydration, the device and how the test is carried out. The most useful approach is to pick one method and use it consistently, so you are comparing like with like. If you need an accurate figure for a medical reason, ask your GP.
Frequently Asked Questions
- How do I calculate body fat percentage with measurements?
- The US Navy method uses a tape measure. For men it needs height, neck and waist; for women it also needs hips. The measurements go into a logarithmic formula that estimates body density and converts it to a body fat percentage. A body fat calculator with measurements does the maths for you, so you only need to measure carefully.
- How accurate is a body fat percentage calculator?
- Tape-measure and BMI-based estimates are rough. They can differ from a DEXA scan or other lab measurement by several percentage points, and the gap varies from person to person. They are most useful for tracking your own trend over time using the same method and the same measuring technique, rather than as a precise number.
- Where exactly do I measure my waist, neck and hips?
- Measure on bare skin with a flexible tape, snug but not squeezing, after breathing out. Measure the neck just below the larynx (Adam's apple). Men measure the waist at the navel; women measure at the narrowest point, which is usually just above the navel. Women measure the hips at the widest part of the buttocks. Repeat each measurement two or three times and use the average.
- Is there a female body fat calculator, and why is it different?
- Yes. The same calculator works for women, but it uses a different formula that includes a hip measurement. Women generally carry more essential body fat than men, so the general guide categories are shifted higher: for example, the guide lists 14 to 20% as athletes for women and 6 to 13% for men. Choose female and the hip field appears.
- What is a healthy body fat level?
- There is no single healthy number. The general guide used on this page lists essential, athletes, fitness, average and above average ranges, which differ for men and women. Healthy levels also vary with age and activity, and very low body fat is not a goal for most people. Your GP can help you interpret your result in the context of your overall health.
- What is a body fat converter, and can I convert BMI to body fat?
- People searching for a body fat converter often want to turn BMI into a body fat percentage, or a percentage into kilograms of fat. The From BMI option estimates body fat from BMI, age and sex using the Deurenberg formula, and the results show fat mass and lean mass in kilograms. Because BMI cannot tell muscle from fat, this estimate is usually less personal than the tape-measure method.
- Why do the two methods give different answers?
- They work from different information. The BMI method only knows your height, weight, age and sex, so two people with the same numbers get the same estimate. The Navy method uses body shape, so it responds to where you carry fat. When both can be calculated, the calculator shows them together; a difference of a few percentage points is common.
- How does estimating body fat compare with DEXA or bioimpedance?
- DEXA scans and bioimpedance devices measure the body more directly, but they have their own limitations: results can vary with hydration, the machine and how the test is done. A tape measure is cheap and easy but less precise. Whichever you use, compare like with like, because switching methods can change the number without any change in your body.
- What do fat mass and lean mass mean?
- Fat mass is your body weight multiplied by your body fat percentage. Lean mass is everything else, including muscle, bone, organs and body water. At 85 kg and 20.9% body fat, for instance, fat mass is about 17.7 kg and lean mass about 67.3 kg. Changes in lean mass matter too, so weight alone does not show what is changing.