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Body Fat Percentage Calculator
Use this free body fat percentage calculator to estimate how much of your body weight is fat and how much is lean tissue. Choose the Navy method, which uses tape measurements of your neck, waist, and hips, or the BMI-based estimate, which needs only your height, weight, and age. The calculator shows your body fat percentage, your fat mass and lean mass, and the category your result falls into.
Measure with a soft tape, level and snug. Waist: at the navel, relaxed, after breathing out. Neck: just below the Adam's apple. Hip: at the widest point.
Body fat categories
| Category | Men | Women |
|---|---|---|
| Essential fat | 2–5% | 10–13% |
| Athletes | 6–13% | 14–20% |
| Fitness | 14–17% | 21–24% |
| Average | 18–24% | 25–31% |
| Obese | 25% and above | 32% and above |
How it works
Body fat percentage is the share of your total body weight that is fat tissue, as opposed to lean mass — muscle, bone, water, and organs. Two people can weigh exactly the same and have very different body fat percentages, which is why body fat is a more useful picture of body composition than weight alone. A 180-pound person at 15 percent body fat carries about 27 pounds of fat, while a 180-pound person at 30 percent carries about 54 pounds of fat, even though the scale shows the same number for both.
The Navy method is the default mode of this calculator. It was developed to estimate body fat quickly with nothing more than a tape measure, and it has held up well against lab methods. For men, the formula is body fat % = 86.010 × log₁₀(waist − neck) − 70.041 × log₁₀(height) + 36.76, with all measurements in inches. For women, the formula is body fat % = 163.205 × log₁₀(waist + hip − neck) − 97.684 × log₁₀(height) − 78.387. The waist minus neck part is the heart of the method: the waist carries the most variable fat, and subtracting the neck corrects for frame size and muscularity. Women carry more fat around the hips, so the hip measurement is added to the waist before the neck is subtracted.
The BMI-based estimate is the fallback mode. It first computes body mass index, BMI = 703 × weight in pounds ÷ height in inches squared, and then applies the Deurenberg formula: body fat % = 1.20 × BMI + 0.23 × age − 10.8 × sex − 5.4, where sex is 1 for men and 0 for women. This mode is handy when you have no tape measure, but it is only a rough estimate, because height and weight alone cannot tell muscle from fat. A muscular person with a BMI of 27 can be estimated at 22 percent body fat by this formula while actually carrying far less.
Once the percentage is known, the calculator splits your weight into fat mass and lean mass. Fat mass is weight × body fat percentage, and lean mass is everything else. If you are tracking a fitness plan, watch lean mass as well as the percentage: holding on to lean mass while fat mass falls means a diet and training plan is working, while a falling percentage caused mostly by lost lean mass is not a win.
The category table above puts your number in context. Essential fat is the minimum the body needs to function, and dropping below it is dangerous. The athlete range is typical of trained competitors, the fitness range of people who train regularly, and the average range covers most adults. In the obese range — 25 percent and above for men, 32 percent and above for women — risks such as type 2 diabetes and heart disease rise clearly, so discuss a result there with a doctor.
Measurement technique matters more than the formula. Measure in the morning, before eating, standing relaxed. Keep the tape level and snug but not compressing the skin, and take each measurement twice, using the average. Measure the waist at the navel after breathing out naturally — do not suck your stomach in — and the neck just below the Adam's apple. Small errors move the result by a full point or more, so measure the same way every time and compare your trend.
Worked example
A man is 70 inches tall, weighs 180 pounds, has a 16-inch neck and a 34-inch waist. He uses the Navy method.
Step 1: Find the waist minus neck — 34 − 16 = 18 inches.
Step 2: Apply the men's Navy formula — body fat % = 86.010 × log₁₀(18) − 70.041 × log₁₀(70) + 36.76.
Step 3: Work out the logs — log₁₀(18) = 1.2553 and log₁₀(70) = 1.8451.
Step 4: Multiply — 86.010 × 1.2553 = 107.97, and 70.041 × 1.8451 = 129.23.
Step 5: Finish — 107.97 − 129.23 + 36.76 = 15.49, which rounds to 15.5%.
His body fat is 15.5%, which falls in the Fitness category for men. His fat mass is 180 × 0.155 = 27.9 pounds, and his lean mass is 180 − 27.9 = 152.1 pounds. If he later re-measures at the same waist and neck but a lower weight, his percentage would barely change, because the Navy formula depends on the tape measurements, not the scale.
FAQ
How accurate is the Navy body fat method?
For most people the Navy method lands within about 3 to 4 percentage points of a lab measurement such as a DEXA scan. It is much more accurate than a BMI-based estimate because it uses your actual body measurements, but tape placement and how tightly you pull the tape can shift the result by a point or two, so measure carefully and take each measurement twice.
Why does the Navy formula use neck and waist measurements?
The waist measurement captures the fat stored around the middle, which is the largest and most variable fat store on the body, while the neck measurement adjusts for overall body frame and muscle. A thick neck relative to the waist usually means a larger, more muscular build, so subtracting the neck from the waist keeps the formula from overestimating body fat on muscular people.
What is a healthy body fat percentage?
For men, the fitness range is roughly 14 to 17 percent and the average range is 18 to 24 percent. For women, the fitness range is roughly 21 to 24 percent and the average range is 25 to 31 percent. Essential fat, the minimum needed for normal body function, is about 2 to 5 percent for men and 10 to 13 percent for women. Athletes, age, and muscle mass all shift what is realistic for one person.
Is the BMI-based estimate as good as the Navy method?
No. The BMI-based estimate is a rough fallback for when you do not have a tape measure. It only uses height, weight, age, and sex, so it cannot tell muscle apart from fat and it regularly overestimates body fat in muscular people and underestimates it in people with little muscle. Use the Navy method whenever you can measure your waist and neck.
How often should I measure my body fat?
Once every two to four weeks is enough. Body fat changes slowly, and daily measurements mostly pick up water, food, and tape-placement differences rather than real change. Measure at the same time of day, under the same conditions, and look at the trend over a few months instead of any single number.