Your weight on the scale does not tell you how much of it is fat and how much is muscle, bone and water. This body fat calculator estimates your body fat percentage with the U.S. Navy method, which needs only a tape measure. Add your weight and it also shows your fat mass and lean body mass.
Quick answer: Men: %BF = 86.010 × log₁₀(waist − neck) − 70.041 × log₁₀(height) + 36.76. Women: %BF = 163.205 × log₁₀(waist + hip − neck) − 97.684 × log₁₀(height) − 78.387 (inches). Example: a man 70 in tall, neck 15 in, waist 34 in → 17.5% (fitness range). Healthy averages: 25–31% for women, 18–24% for men.
How to measure for the body fat calculator
- Use a flexible tape measure and stand relaxed; do not hold your breath or pull in your stomach.
- Neck: just below the Adam’s apple, tape sloping slightly down to the front.
- Waist: men at the navel; women at the narrowest point.
- Hips (women): at the widest part of the buttocks.
- Height: without shoes, in inches (5 ft 10 in = 70 in) or centimeters.
- Enter the numbers, choose your sex and press Calculate.
Body fat percentage chart
| 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 |
Source: American Council on Exercise.
Body fat calculation examples
Example 1: man, 70 in, neck 15 in, waist 34 in, 180 lb
- 86.010 × log₁₀(34 − 15) − 70.041 × log₁₀(70) + 36.76 = 17.5% → Fitness
- Fat mass = 180 × 0.175 ≈ 31.5 lb; lean mass ≈ 148.5 lb
Example 2: woman, 65 in, neck 13 in, waist 30 in, hips 38 in
- 163.205 × log₁₀(30 + 38 − 13) − 97.684 × log₁₀(65) − 78.387 = 28.6% → Average
Example 3: the same man in metric
177.8 cm, neck 38.1 cm, waist 86.36 cm gives the same 17.5%: the calculator converts centimeters to inches before applying the formula.
How to read your result
- Look at the trend. A change of 1–2 points over a few months says more than a single reading.
- Compare with BMI. If your BMI is high but your body fat is in the fitness range, much of your weight is muscle.
- Waist-to-height ratio. The calculator also shows your waist divided by your height. Keeping it under 0.5 is a simple target linked with lower health risk.
- Plan your calories. To lose fat at a steady pace, find your maintenance calories with the calorie calculator and aim for a moderate deficit.
- Need centimeters? Convert your tape measurements with the length converter.
Common mistakes
- Measuring the waist in the wrong place. Men measure at the navel, not the narrowest point.
- Pulling the tape too tight. Snug, not compressing the skin.
- Measuring after a meal or workout. Bloating and pump change your waist and neck.
- Comparing with a different method. Smart scales, calipers and DEXA scans give different numbers; compare like with like.
This calculator gives an estimate for adults and is not a medical assessment. Ask your doctor about what a healthy body composition means for you.
Frequently asked questions
How do you calculate body fat percentage?
The U.S. Navy method uses a tape measure. For men: 86.010 × log10(waist − neck) − 70.041 × log10(height) + 36.76, with all measurements in inches. For women: 163.205 × log10(waist + hip − neck) − 97.684 × log10(height) − 78.387. A man who is 70 in tall with a 15 in neck and a 34 in waist comes out at 17.5%.
What is a healthy body fat percentage?
The American Council on Exercise considers 21–24% fit and 25–31% average for women, and 14–17% fit and 18–24% average for men. Obesity starts at 32% for women and 25% for men. Women naturally carry more essential fat (10–13%) than men (2–5%).
How accurate is the Navy body fat calculator?
Studies comparing it with lab methods such as DEXA usually find it within about 3–4 percentage points for most people. It works best when you measure carefully: same time of day, relaxed posture, tape snug but not compressing the skin. Average three measurements.
Where do I measure my waist and neck?
Measure your neck just below the larynx (Adam’s apple), with the tape sloping slightly downward toward the front. Men measure the waist at the navel; women measure at the narrowest point of the waist. Women also measure the hips at the widest part of the buttocks.
Is body fat percentage better than BMI?
Body fat percentage tells you what your weight is made of; BMI only compares weight with height. A muscular person can have a high BMI and low body fat. For most people the two agree, so using both gives a fuller picture than either alone.
How do I calculate lean body mass?
Lean body mass is your weight minus your fat mass. At 180 lb and 17.5% body fat, fat mass is 180 × 0.175 ≈ 31.5 lb, so lean mass is about 148.5 lb. Enter your weight in the calculator to see both numbers.
What body fat percentage shows abs?
Visible abdominal muscles usually appear around 10–12% body fat for men and 16–19% for women, though genetics and where you store fat make a big difference.
How fast can I lower my body fat?
A sustainable rate is about 0.5–1% of body weight per week. Combining a moderate calorie deficit with strength training and enough protein helps you lose fat while keeping muscle.
Last updated: