FitCalculationBody fat percentage is the share of your total body weight that comes from fat rather than lean tissue such as muscle, bone, and water. A body fat calculator estimates that percentage from measurements you take yourself, which gives you a picture of body composition rather than weight alone.
Body Fat Calculator
Estimate your body fat percentage, fat mass, and lean body mass with the U.S. Navy circumference method.
What this calculates
Height plus tape measurements around the neck, waist and - for women - hips, entered into the published circumference equation.
What is a body fat calculator?
This calculator estimates your body fat percentage from tape measurements using the U.S. Navy circumference method. It then uses your body weight to turn that percentage into two useful figures: fat mass in kilograms and lean body mass in kilograms.
The result is an estimate, not a direct measurement of body fat. Methods that measure body composition directly, such as DEXA, work differently and will not always agree with a circumference estimate.
U.S. Navy body fat calculator
The U.S. Navy circumference method estimates body fat percentage from tape measurements taken at specific sites. This calculator uses:
- Heightincluded
- Neck circumferenceincluded
- Waist circumferenceincluded
- Hip circumferencewomen only
Weight and age are not equation inputs
The Navy body fat equation does not use your weight or your age. The calculator collects them so the form matches the other calculators on this site, and weight is then used to convert the percentage into fat mass and lean body mass. Changing your weight on its own does not change the percentage.
Sex selects the equation
The method has a male version and a female version. The female version adds the hip measurement, which is why the hip field appears only after you select Female.
Body fat formula
The male and female versions of the U.S. Navy equation estimate body fat percentage from your height and circumference measurements:
Men: BF% = 495 / (1.0324 − 0.19077 × log10(waist − neck) + 0.15456 × log10(height)) − 450
Women: BF% = 495 / (1.29579 − 0.35004 × log10(waist + hip − neck) + 0.22100 × log10(height)) − 450
Measured in centimetres
Height and every circumference are converted to centimetres before the formula is applied, so the result is the same whether you enter your measurements in centimetres or in inches.
Reading the formula
log10 means the base-10 logarithm, and BF% is the estimated body fat percentage. The equation takes the logarithm of the difference between your measurements, which is why a waist measurement has to be larger than a neck measurement for the calculation to work.
How to measure for the calculator
How to measure body fat percentage with a tape comes down to technique. The equations assume a level tape and consistent placement, so measure against the skin at the end of a normal exhale, keep the tape snug without pulling it tight, and take each site two or three times until the numbers agree.
How to measure your neck
Stand relaxed, look straight ahead, and measure just below the larynx. Let the tape slope slightly downward at the front of the neck, and do not tuck your chin in or tense your neck muscles.
How to measure your waist
Men measure at the level of the navel and women measure at the narrowest point of the waist. Keep the tape level the whole way around, breathe out normally, and check the reading a second time before you enter it.
How to measure your hip
Women measure around the widest point of the hips and buttocks with the feet together and the tape level. This measurement is used by the female equation only, so it is not needed if you select Male.
Body fat calculator for men and women
The tape measurements the method needs depend on your sex:
- Menneck + waist
- Womenneck + waist + hip
Both versions also use your height. The two equations were developed separately from measurements taken on men and on women, and the female version includes the hip measurement as an extra input — it is not the male equation with a different number at the end.
So a body fat calculator for women asks for one more tape measurement than the same calculator for men. Everything else works the same way: you enter your height and circumference measurements, they are converted to centimetres, and the equation returns an estimated percentage that is then turned into fat mass and lean body mass.
Army, Navy, and military body fat calculators
Armed services assess body composition because weight relative to height on its own does not describe body composition. Several of those assessments are based on circumference measurements taken with a tape, and each service sets its own procedures: the measurement sites, rounding, and the equations or tables applied can differ between services and can change over time.
This calculator is not an official Army, Marine Corps, Navy, or other military calculator. It applies the U.S. Navy circumference equations and nothing else, and it does not use any service's scoring or body composition limits. An army body fat calculator, a USMC body fat calculator, or another military body fat calculator may use different measurements or a different standard and produce a different number.
If you need to meet a service standard, use the current official documentation from that service rather than an online estimate.
How accurate is the Navy body fat calculator?
The Navy method is an estimate worked out from measurements, not a direct measurement of body fat. How accurate your result is therefore depends heavily on how the tape measurements are taken: a small difference at the neck, waist, or hip changes the percentage, and inconsistent placement between attempts can make two readings of the same body disagree.
Limits of circumference equations
The equations were built from measurements taken across groups of people, so they model a population rather than an individual. Two people with identical measurements do not necessarily carry the same amount of fat, and very muscular or very lean bodies are not always described well by a tape measurement.
Comparing results over time
Because of those limits, a result from this calculator can differ from other body-composition methods, and different methods should not be expected to match exactly. Measuring under similar conditions each time — the same tape placement, the same point in your day, the same breathing — makes your own readings easier to compare.
Body fat calculator vs calipers and other methods
A tape measure is one of several ways to estimate body fat. Other options include:
- Skinfold calipersskinfold thickness
- Bioelectrical impedancescales and monitors
- DEXAclinical scan
These methods estimate or measure body composition in different ways. Calipers measure the thickness of skinfolds at selected sites, bioelectrical impedance passes a small current through the body, and DEXA uses a low-dose scan to separate tissue types. Each one relies on different assumptions, so results should not be expected to match exactly.
This calculator uses tape measurements only. Whichever method you choose, comparing your own readings from the same method over time is usually more useful than comparing a number from one method with a number from another.
Body Fat FAQ
How accurate is the Navy body fat calculator?
It is an estimate rather than a direct measurement of body fat. Its results depend on how consistently you take the tape measurements, and circumference equations cannot describe every body type, so a reading can differ from methods such as DEXA. Measuring the same way each time makes your own numbers easier to compare.
How do I measure my neck for the body fat calculator?
Stand relaxed and look straight ahead, then measure just below your larynx with the tape sloping slightly downward at the front of the neck. Keep the tape snug without pulling it tight, and do not tuck your chin in.
How do I measure my waist for the body fat calculator?
Men measure at the level of the navel and women measure at the narrowest point of the waist. Keep the tape level the whole way around, breathe out normally, and repeat the measurement two or three times to check it is consistent.
What is the difference between a Navy and Army body fat calculator?
Both can start from circumference measurements, but services that use tape-based assessments set their own procedures, and those procedures can change. This calculator applies the U.S. Navy circumference equations only. It is not an official Army or military calculator and it does not apply any service's standards.
What is my body fat percentage?
There is no figure you can look up, because it depends on your own measurements. Enter your sex and height with your neck and waist measurements — plus your hip measurement if you select Female — and the calculator estimates your body fat percentage with the U.S. Navy equation, then shows your fat mass and lean body mass as well.
What is a healthy body fat percentage?
There is no single number that suits everyone. Reference ranges differ between men and women, shift with age, and vary between the organisations that publish them, and body fat percentage is only one part of health alongside fitness, muscle mass, and measures such as waist circumference. This calculator does not label a result as healthy or unhealthy; if you want your own figure interpreted, speak to a healthcare professional.
How is body fat percentage calculated?
This calculator uses the U.S. Navy circumference equation, which takes the base-10 logarithm of the difference between your measurements — waist minus neck for men, and waist plus hip minus neck for women — together with your height. Height and every circumference are converted to centimetres before the formula is applied, and your weight is then used to work out fat mass and lean body mass.
Why does the calculator need my hip measurement?
The female version of the U.S. Navy equation includes hip circumference as an input, while the male version does not use it at all. That is why the hip field only appears once you select Female: it is required for the female equation, and it is ignored if you select Male.
How often should I measure my body fat?
Body fat changes slowly, so measuring every few weeks or about once a month usually tells you more than measuring every day. Because tape measurements vary with technique, take your readings at roughly the same time of day and in the same way each time, and compare readings over a period rather than judging a single result.
What is the difference between body fat percentage and BMI?
Body fat percentage estimates how much of your weight comes from fat, while BMI compares your weight with your height. They are different measures: BMI is a quick screening value that does not distinguish fat from muscle, so two people with the same BMI can have very different body composition, while body fat percentage here is estimated from tape measurements rather than measured directly. Neither figure describes everything about health on its own.