Body Fat Calculator
This calculator estimates body fat percentage from your height and a few tape measurements, using the method developed for the US Navy. It also splits your weight into fat mass and lean mass.
Type a number and the answer appears straight away.
Body fat (US Navy method)17.9%Fitness
- Essential under 6
- Athletes 6-14
- Fitness 14-18
- Average 18-25
- Obese 25+
- Fat mass
- 28.6 lb
- Lean body mass
- 131.4 lb
The math behind it: Body Fat
Men: 495 / (1.0324 - 0.19077 x log10(waist - neck) + 0.15456 x log10(height)) - 450 (measurements in cm)
For women the formula adds the hip measurement: 495 / (1.29579 - 0.35004 x log10(waist + hip - neck) + 0.22100 x log10(height)) - 450.
How to take the measurements
- Neck: measure just below the larynx (Adam's apple), with the tape sloping slightly down toward the front. Keep your shoulders relaxed.
- Waist: men measure horizontally at the navel; women measure at the narrowest point of the torso. Breathe out normally and do not pull your stomach in.
- Hips (women only): measure around the widest part of the buttocks, keeping the tape level.
- Take each measurement two or three times and use the average, rounding to the nearest quarter inch or half centimeter.
Body fat categories
The American Council on Exercise groups body fat percentages into the following ranges. Women naturally carry more essential fat than men.
| Category | Women | Men |
|---|---|---|
| Essential fat | 10-13% | 2-5% |
| Athletes | 14-20% | 6-13% |
| Fitness | 21-24% | 14-17% |
| Average | 25-31% | 18-24% |
| Obese | 32% and above | 25% and above |
What body fat is
Body fat is not just stored energy. Essential fat cushions organs, insulates the body and is needed to produce hormones. Storage fat sits under the skin (subcutaneous fat) and around the organs in the abdomen (visceral fat). Visceral fat is the type most strongly linked with heart disease and type 2 diabetes, which is why waist size features in this method.
Both too much and too little fat carry health risks. Dropping to or below the essential range can disrupt hormones, bone health and immunity.
How accurate is the Navy method?
The equations were published by Hodgdon and Beckett at the Naval Health Research Center in 1984. For most people the result is within about 3 to 4 percentage points of laboratory methods. It is least reliable for very lean, very muscular or very heavy individuals, and it depends heavily on careful measuring.
More precise options include DEXA scanning, hydrostatic (underwater) weighing and air-displacement plethysmography. Bathroom scales that estimate body fat use bioelectrical impedance, which varies with hydration.
Fat mass and lean mass
Fat mass is your weight multiplied by your body fat percentage. Lean mass is everything else: muscle, bone, organs and water. Tracking the two separately is more informative than weight alone, because a program that builds muscle while reducing fat may barely move the scale.
Common questions
What is a healthy body fat percentage?
Ranges often quoted as healthy are roughly 21% to 33% for women and 8% to 19% for men aged 20 to 39, rising a little with age.
Is body fat percentage better than BMI?
It answers a different question. BMI only compares weight with height; body fat percentage estimates how much of that weight is fat, so it is more informative for muscular or older people.
Read more about this
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