Body Fat Calculator
Estimate your body fat percentage with the US Navy tape-measure method — more telling than BMI. Enter a few measurements to see your body-fat percentage, your ACE fitness category on a visual gauge, and your fat and lean mass in pounds and kilograms.
17.5% body fat — Fitness
Fat mass: 30.8 lb · Lean mass: 145.2 lb
US Navy circumference method (Hodgdon & Beckett). An estimate, not a clinical measurement like DEXA — accuracy varies and it can read high or low at the extremes. How we calculate →
How the US Navy body fat method works
The US Navy method estimates body fat from a few tape-measure circumferences rather than weight alone, which is why it's more useful than BMI for body composition. Men measure neck and waist (at the navel); women add the hips. Those numbers, with your height, go into the Navy formula to give a body-fat percentage. Enter your measurements above in inches or centimetres and the result updates instantly.
It's the same method the US Navy uses for fitness standards — quick, free and reasonably accurate for most people, though not a substitute for a clinical scan.
Reading your body fat percentage
Your result is plotted on the American Council on Exercise (ACE) scale. For men: essential fat 2–5%, athletes 6–13%, fitness 14–17%, average 18–24%, and 25%+ is classed as obese. For women, who carry more essential fat: essential 10–13%, athletes 14–20%, fitness 21–24%, average 25–31%, and 32%+ obese. The gauge above shows which band you fall into.
Fat mass and lean mass
Once you know your body-fat percentage, the calculator splits your weight into fat mass and lean mass (everything else — muscle, bone, organs, water), shown in both pounds and kilograms. Tracking lean mass is useful when you're dieting or training: the goal is usually to lose fat while keeping lean mass, which the scale weight alone can't tell you.
Body fat vs BMI
BMI uses only height and weight, so it can misjudge muscular or lean people. Body-fat percentage measures composition directly, which is why a muscular athlete can have a 'high' BMI but a healthy body-fat reading. The two are complementary: BMI is a fast screen, body fat is a closer look. For the fullest picture, check both alongside your waist measurement.
How to measure accurately
Use a flexible tape and keep it level and snug, not tight. Measure your neck just below the larynx, your waist at the navel (men) or at the narrowest point (women), and your hips at the widest point (women). Measure relaxed, not flexing or holding your breath, and take each measurement twice. Small errors in the tape change the result, so consistency matters more than a single perfect reading.
Limits of the estimate
No tape-measure method is as precise as a DEXA scan or hydrostatic weighing. The Navy formula can read a little high for very lean people and a little low for some others, and it doesn't account for where fat sits. Treat the number as a useful estimate to track over time rather than an exact figure — the trend matters more than any single reading.
Frequently asked questions
How do I calculate my body fat percentage?
The US Navy method uses tape measurements: neck and waist for men, plus hips for women, along with your height. The calculator above applies the Navy formula to those numbers and returns your body-fat percentage instantly, with your category and fat/lean mass.
What is a healthy body fat percentage?
On the ACE scale, a 'fitness' level is about 14–17% for men and 21–24% for women, while 'average' is 18–24% and 25–31% respectively. Essential fat (the minimum) is around 2–5% for men and 10–13% for women. The gauge above shows your band.
How accurate is the US Navy body fat method?
It's reasonably accurate for most people and far better than BMI for composition, but it's an estimate — typically within a few percentage points of a DEXA scan. It can read high for very lean people. Measure carefully and track the trend rather than a single number.
What's the difference between body fat and BMI?
BMI uses only height and weight and can misclassify muscular people; body-fat percentage measures composition directly. A muscular person may have a high BMI but a healthy body-fat reading. Use both together for a fuller picture.
How do I measure my waist and neck correctly?
Use a flexible tape kept level and snug. Measure the neck just below the larynx and the waist at the navel for men or the narrowest point for women; women also measure hips at the widest point. Stay relaxed and measure twice for consistency.
What is lean body mass?
Lean body mass is your weight minus your fat mass — muscle, bone, organs and water. The calculator shows it in pounds and kilograms. Keeping lean mass while losing fat is the usual goal of a good diet and training plan.
Is the calculator different for men and women?
Yes. Women carry more essential fat, so the Navy formula adds the hip measurement and the ACE category ranges are higher. Select your sex above and the correct formula and scale are applied automatically.
Can body fat percentage be too low?
Yes — below the essential-fat level (about 2–5% for men, 10–13% for women) the body can't function properly, which is unhealthy. Very low body fat should only be approached under professional guidance.
Researched & verified by the Calcuris Data & Research Team. How we build and check our tools →