Body Fat Percentage Calculator for Men
The bathroom scale tells you weight; it cannot tell you what the weight is. This free body fat percentage calculator for men uses the U.S. Navy method, the tape measure formula the American military uses, to estimate your body fat percentage from height, neck and waist measurements (women: add hips). It also shows your category, fat mass and lean mass, so you can track actual fat loss instead of watching the scale wobble. Uses the US Navy circumference method, tape measurements at the waist, neck and hips, no calipers or lab visit needed.
Last updated: October 22, 2026
Your result
The formula
Men: BF% = 495 ÷ (1.0324 − 0.19077 × log₁₀(waist − neck) + 0.15456 × log₁₀(height)) − 450Women: BF% = 495 ÷ (1.29579 − 0.35004 × log₁₀(waist + hip − neck) + 0.22100 × log₁₀(height)) − 450Measure every circumference in the same units (cm or inches); the formula works with either.Fat mass = weight × BF% ÷ 100, and lean mass = weight − fat mass.
A worked example
A man 180 cm tall weighing 90 kg, with a 40 cm neck and an 85 cm waist, gets a body fat reading of about 14.5%, which falls in the Fitness category, roughly 13.1 kg of fat mass and 76.9 kg of lean mass.
More about the Body Fat Calculator
What body fat percentage means
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 while one carries far more fat, which is why the percentage tells you what the bathroom scale cannot: whether a change in weight came from fat, muscle or water.
Not all body fat is excess. Essential fat, the minimum your body needs for hormones, organ protection and basic function, is about 2 to 5% for men and 10 to 13% for women, and dropping near those floors is dangerous. Everything above essential fat is storage fat: useful as an energy reserve in moderation, a health risk when it accumulates. The Navy method estimates where you sit on that spectrum from a few tape measurements.
How the Navy method estimates body fat
A worked example. A man, 180 cm, 90 kg, 40 cm neck, 85 cm waist: the Navy formula returns about 14.5% body fat, squarely in the Fitness category. That breaks down to roughly 13.1 kg of fat mass and 76.9 kg of lean mass. Now the useful part: three months later he is 88 kg at 13%, the scale says 2 kg lost, but the calculator says fat mass dropped from 13.1 to about 11.4 kg while lean mass held. That is the story the scale alone could never tell.
The formula itself, demystified: for men it combines waist minus neck with height through logarithms; for women, waist plus hip minus neck. The waist to neck gap is doing most of the work. It is a proxy for central fat. That is also why measurement consistency matters so much: a 2 cm difference in waist measurement, from measuring after lunch versus before breakfast, can move the result a full percentage point. Same time of day, same tape tension, monthly.
Accuracy limits and tracking change over time
Tips for tracking that actually works. Measure monthly, not weekly, body fat changes slowly and weekly noise will only demoralise you. Log the raw measurements, not just the percentage; if the percentage stalls but the waist shrinks, you are still winning. Pair it with the scale and a waist photo: three imperfect measures beat one. And re measure after any big weight change, since the formula's accuracy shifts as composition changes.
The honest limits: an estimate, not a diagnosis, within a few points of DEXA for most people, less reliable at the extremes of muscularity or leanness. It says nothing about visceral versus subcutaneous fat, which is the medically important distinction. These are estimates for healthy adults, not medical advice; if the number worries you, a doctor or dietitian, not a calculator, is the next step.
How to use the Body Fat Calculator
- Choose your gender and metric or imperial units.
- Enter your height, neck and waist measurements (plus hip for women), along with your weight.
- Press Calculate to see your body fat percentage, category, fat mass and lean mass.
- Measure at the same time of day and re check monthly to track real progress.
Frequently asked questions
How accurate is the Navy method, honestly?
Typically within 3 to 4 percentage points of a DEXA scan, among the best free estimates you can do at home. It is most reliable for average builds; very muscular athletes and people with unusual fat distribution get less reliable numbers. Treat it as a trend tracker, not a medical measurement: the direction over months matters more than any single reading.
What counts as a healthy body fat percentage?
It depends on sex, but the broad healthy bands are well established. For men, essential fat is 2 to 5% and a healthy active range runs roughly 6 to 24%; for women, essential fat is 10 to 13% with a healthy range around 14 to 31%. At or above 25% for men or 32% for women is classed as obese, and that is the line where health risks clearly start climbing, whatever the scale says. Dropping near essential fat levels is dangerous for anyone; the body needs fat to function.
Where exactly do I put the tape?
Neck just below the Adam's apple, waist at the navel, hips at the widest point. Tape snug against skin without pressing in, breathe out normally, do not suck in your stomach. Measure in the morning, monthly, under the same conditions, consistency of method beats precision of any single measurement.
Why does this disagree with my smart scale?
Smart scales use bioelectrical impedance, which swings several points with hydration, meals and time of day, fine for trends, shaky for absolute numbers. The Navy method depends only on tape measurements, so it is more repeatable. For true precision, a DEXA scan is the gold standard; for tracking progress at home, the tape wins.
I am quite muscular. Will this work for me?
Honestly, not as well. The formula was built around average body composition, so a heavily muscled build tends to read higher than it is, a thick neck and waist from muscle rather than fat push the number up. If you lift seriously, follow the trend and the mirror instead of stressing over the absolute percentage.
Why is body fat percentage more useful than weight alone?
Because the scale is blind to composition, it cannot tell what you actually lost or gained. Two people can weigh exactly the same while one carries far more fat, and during a diet the scale can stall while fat keeps dropping if you are adding muscle. Body fat percentage tracks the change you actually care about. That is why athletes watch it instead of the scale.
What is the US Navy body fat formula?
For men, using inches: 86.010 x log10(waist, neck) - 70.041 x log10(height) + 36.76. For women: 163.205 x log10(waist + hip, neck) - 97.684 x log10(height) - 78.387. The tape measure inputs are the whole method, the math just converts circumferences into a body fat estimate that usually lands within 3 to 4 percentage points of a DEXA scan.
Why does the calculator ask for my neck measurement?
The neck measurement corrects for frame size. Two people with the same waist and height can carry very different amounts of fat, a thick neck signals a bigger overall frame, so the formula subtracts neck size before judging the waist. Measure just below the Adam's apple (or at its narrowest for women), tape snug but not tight, looking straight ahead.
How often should I measure my body fat?
Every 2 to 4 weeks, under identical conditions: same time of day, before eating, after using the bathroom. The tape method has about a 1% wiggle from measurement to measurement, so weekly readings just show noise. Monthly readings on the same routine show the real trend, and always measure before a workout, not after, when muscles are pumped.
How do I calculate body fat percentage at home?
Use the US Navy tape method. Men: 86.010 × log10(waist − neck) − 70.041 × log10(height) + 36.76. Women: 163.205 × log10(waist + hip − neck) − 97.684 × log10(height) − 78.387. Measure in inches or centimeters and plug into our calculator for an instant result accurate to within about 3 to 4%.