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Body Fat Calculator

Estimate your body fat percentage with a tape measure using the US Navy method, plus fat mass and lean mass.

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Body Fat Calculator Nothing is stored or sent

For general information only, not medical advice. Results are estimates and do not replace a check-up with a doctor or other qualified health professional.

What your result means

Body fat percentage is the share of your total weight that is fat. The calculator places your result in one of the five categories used by the American Council on Exercise (ACE). Women naturally carry more fat than men, so the ranges are different for each sex.

Category Women Men
Essential fat 10 to 13% 2 to 5%
Athletes 14 to 20% 6 to 13%
Fitness 21 to 24% 14 to 17%
Average 25 to 31% 18 to 24%
Obese 32% and above 25% and above

These bands are a guide, not a diagnosis. A result in the “Average” band is common, and a result in the “Athletes” band is not a goal for everyone. Very low body fat can be as harmful as very high body fat.

How body fat is calculated

The calculator uses the US Navy circumference method, published by Hodgdon and Beckett at the Naval Health Research Center in 1984. It predicts body fat from a few tape measurements and your height. All lengths are in centimetres. If you choose imperial, inches are converted to cm first.

Formula for men

Body fat % = 495 ÷ (1.0324 − 0.19077 × log10(waist − neck) + 0.15456 × log10(height)) − 450

Formula for women

Body fat % = 495 ÷ (1.29579 − 0.35004 × log10(waist + hip − neck) + 0.22100 × log10(height)) − 450

  • Waist, hip and neck: your measurements in cm. A larger waist (and hip, for women) compared with your neck means more body fat.
  • Height: your height in cm. Taller people carry the same waist size over a bigger frame.
  • log10: the base-10 logarithm. You do not need to work this out; the calculator does it.
  • 495 and 450: fixed numbers that turn estimated body density into a body fat percentage.

The result is shown to one decimal place. If you enter your weight, the calculator also shows fat mass = weight × body fat % and lean mass = weight − fat mass. Lean mass is everything that is not fat: muscle, bone, organs and water.

How to use the body fat calculator

  1. Choose your sex and pick metric (cm, kg) or imperial (ft, in, lb).
  2. Enter your height, then your neck and waist measurements. Women also enter their hip measurement.
  3. Optionally, enter your weight to see your fat mass and lean mass.
  4. Read your body fat percentage and ACE category. The result updates as you type.

How to measure correctly

Small tape errors change the result, so measure carefully. Use a soft, non-stretch tape. Keep it snug but not pressing into the skin. Stand relaxed and breathe out normally before you read the number.

  • Neck: just below the larynx (Adam’s apple), with the tape sloping slightly down towards the front.
  • Waist (men): around the belly at the level of the navel.
  • Waist (women): at the narrowest point of the waist, usually above the navel.
  • Hip (women): around the widest part of the buttocks.

Measure at the same time of day, ideally in the morning before eating, and take each measurement twice. If the two readings differ, use the average.

Worked example

A man is 175 cm tall, with a 38 cm neck and a 90 cm waist. He weighs 80 kg.

  1. Waist − neck = 90 − 38 = 52. log10(52) = 1.7160.
  2. log10(175) = 2.2430.
  3. Bracket: 1.0324 − (0.19077 × 1.7160) + (0.15456 × 2.2430) = 1.0517.
  4. 495 ÷ 1.0517 = 470.66. Then 470.66 − 450 = 20.7% body fat.
  5. Fat mass: 80 × 20.7% = about 16.5 kg. Lean mass: about 63.5 kg.

At 20.7%, he falls in the ACE “Average” range for men (18 to 24%). For comparison, a woman who is 162 cm tall, with a 33 cm neck, 76 cm waist and 98 cm hip, gets 29.8%, which is also in the “Average” range for women (25 to 31%).

Body fat percentage vs BMI

BMI uses only height and weight. It cannot tell muscle from fat. A muscular cricketer and an inactive office worker can have the same BMI but very different body fat. Body fat percentage, together with your waist size, tells you more about where your weight comes from.

That said, BMI is still useful for quick screening. Many people use both: check your BMI with the BMI calculator, then use this tool to see whether extra weight is fat or muscle.

Body fat in Indians and South Asians

South Asians tend to carry more body fat, especially around the belly, than white Europeans at the same BMI. This is why a WHO expert group (opens in new tab) suggested lower BMI action points for Asian populations, and why India’s 2009 consensus guideline treats a BMI of 23 or more as overweight.

India now has body fat cut-offs too. The 2025 revised definition of obesity for Asian Indians (opens in new tab), written by an expert group including doctors from AIIMS New Delhi, defines obesity as body fat above 25.5% in men and above 38% in women. It also says body fat should decide the matter in the rare person whose BMI is below 23 but whose fat is above these limits. Note that these limits do not line up with the ACE bands in the calculator, which call 25% (men) and 32% (women) obese. The Indian limits were set for diagnosing disease risk, ACE’s for fitness.

A tape measure around your waist is a simple check as well. Indian guidelines treat a waist of 90 cm or more in men and 80 cm or more in women as abdominal obesity, which is linked to a higher risk of type 2 diabetes and heart disease, even at a “normal” BMI.

How to lower your body fat safely

  • Eat in a small calorie deficit. Aim to lose about 0.5 kg a week. Find your daily target with the calorie calculator.
  • Get enough protein. Dal, eggs, paneer, curd, fish, chicken and soy help you keep muscle while losing fat.
  • Do strength training 2 to 3 times a week. It protects muscle, so more of the weight you lose comes from fat.
  • Stay active every day. Walking counts. WHO guidelines (opens in new tab) advise adults to get 150 to 300 minutes of moderate activity each week.

You cannot burn fat from one spot. Sit-ups strengthen your stomach muscles but do not burn belly fat on their own. Fat comes off the whole body over time.

Limitations

The US Navy method is an estimate, and it tends to read low. The Navy equations were built in 1984 against underwater weighing, not modern scans. In a 2023 study of 1,407 US Army recruits (opens in new tab), the military’s tape-measure equations gave body fat about 6 percentage points lower than a DXA scan on average. Over 8 weeks of training, DXA showed recruits losing 3 to 4 points of body fat, while the tape method missed most of the change in men and all of it in women.

So read your result as a rough band, not an exact number. Track it over months rather than weeks, and pair it with your waist size and weight. If you need an accurate figure, ask your doctor about a DXA (also called DEXA) body composition scan.

  • It is less accurate for very lean or very muscular people, and for people with obesity.
  • It is not designed for children, teenagers or pregnant women.
  • Swelling, bloating or recent large meals can change your waist size.
  • The formula was built mainly on Western adults, so results may be less accurate for some ethnic groups.

See a doctor if your body fat or waist size is high and you also have high blood pressure, high blood sugar or a family history of heart disease. Also see a doctor about unexplained weight loss or very low body fat with missed periods, tiredness or dizziness.

Key facts

FAQ

Body Fat Calculator FAQs

What is a healthy body fat percentage?

For most adults, a healthy body fat percentage is about 21 to 31% for women and 14 to 24% for men, the ACE “Fitness” and “Average” bands. ACE classes 32% or more (women) and 25% or more (men) as obese. India’s 2025 obesity definition uses more than 38% for women and more than 25.5% for men. Compare your result with your own past readings too.

How accurate is the US Navy body fat method?

The US Navy method is a rough estimate that tends to read low. In a 2023 study of 1,407 US Army recruits, tape-measure equations gave about 6 percentage points less body fat than a DXA scan on average, and missed much of the change over 8 weeks. Errors grow if the tape is placed wrongly. Use it as a band and track it over months.

Where exactly should I measure my neck, waist and hips?

Measure your neck just below the Adam’s apple, with the tape sloping slightly down at the front. Men measure the waist at the navel; women measure it at the narrowest point. Women measure the hip at the widest part of the buttocks. Keep the tape snug but not tight, stand relaxed and read it after breathing out normally.

Is body fat percentage better than BMI?

Body fat percentage tells you more than BMI because it separates fat from muscle, while BMI uses only height and weight. A muscular person can have a high BMI but low body fat. BMI is still a quick and useful screening tool, so many doctors use both, along with waist size, to judge health risk.

Why do women have higher body fat than men?

Women have higher body fat than men because their bodies need more essential fat for hormones, periods, pregnancy and breastfeeding. Essential fat is about 10 to 13% in women compared with 2 to 5% in men. Women also tend to store more fat around the hips and thighs, while men store more around the belly. That is why the ranges differ by sex.

How can I reduce my body fat percentage?

You reduce body fat by eating slightly fewer calories than you burn, eating enough protein and doing strength training two or three times a week. Daily movement, such as walking, also helps. Aim to lose about 0.5 kg a week, within the 0.5 to 1 kg the NHS advises. You cannot burn fat from one body part by exercising that part alone.

What is essential fat?

Essential fat is the minimum fat your body needs to work normally. It is found in nerves, the brain, bone marrow and around organs, and it helps control hormones and body temperature. ACE puts it at about 10 to 13% of body weight for women and 2 to 5% for men. Going below these levels can harm your health.

How often should I measure my body fat?

Measuring body fat once a month is enough for most people. Body fat changes slowly, and the tape method misses small changes, so daily or weekly readings mostly show tape errors and water changes. Measure at the same time of day, ideally in the morning before eating, with the same tape and the same method, so your results are easy to compare.