Body Fat Calculator: Find Your Body Fat Percentage With a Tape Measure
Measure your neck and waist (and hips) to get your body fat percentage, fat and lean mass, and how you compare with healthy ranges for your age and sex.
Step 1
Men and women store fat differently, so the formula and healthy ranges are different.
Step 2
A healthy body fat level rises a little with age.
Please enter an age between 18 and 100. These formulas aren't designed for children or teens.
Step 3
Used to work out how many pounds of fat and lean mass you carry.
Please check your numbers. Height should be 4′7″–7′3″ (140–220 cm) and weight 70–600 lb (32–272 kg).
Last step · Grab a tape measure
Neck: just below your Adam's apple, with the tape sloping slightly down at the front.
Waist: level with your belly button,at the narrowest point of your waist, relaxed, after breathing out.
Hips: around the widest part of your buttocks.
Keep the tape snug but not tight, and stand up straight.
Please check your measurements. Your waist should be bigger than your neck, and every number should be realistic (neck 10–25 in, waist 20–80 in, hips 25–80 in).
Calculating your body fat…
Your body fat percentage says much more about your health than your weight or BMI does, and you can estimate it at home with a tape measure. This body fat calculator uses the U.S. Navy method (neck, waist and, for women, hips) to give your body fat percentage, how many pounds of fat and lean mass you carry, and how you compare with healthy ranges for your age and sex. No tape measure? It can also give a rough estimate from your BMI.
How to measure for the most accurate result
- Neck: just below the Adam’s apple (larynx), with the tape sloping slightly downward at the front.
- Waist (men): horizontally, level with your belly button, relaxed, at the end of a normal breath out.
- Waist (women): at the narrowest point of your waist, usually just above the belly button.
- Hips (women): around the widest part of your buttocks, with feet together.
Use a flexible tape, keep it snug but not compressing the skin, and measure each spot twice. Measure at the same time of day (morning is best), because meals and water shift your waist.
How the calculator works
The U.S. Navy formula was developed by Hodgdon and Beckett in 1984 from hundreds of Navy personnel whose body fat was measured by underwater weighing. It uses the fact that fat collects around the waist (and hips in women), while neck size tracks your frame and muscle:
- Men: % body fat = 86.010 × log10(waist − neck) − 70.041 × log10(height) + 36.76
- Women: % body fat = 163.205 × log10(waist + hip − neck) − 97.684 × log10(height) − 78.387
All measurements are in inches. From your body fat percentage, we work out your fat mass (weight × body fat %) and lean mass (everything else: muscle, bone, organs and water). If you skip the tape, we use the Deurenberg equation, which estimates body fat from BMI, age and sex. It’s quick but less accurate, especially for muscular people.
Body fat percentage chart
These healthy ranges come from a study by Gallagher and colleagues that linked body fat to the standard BMI categories. Healthy levels rise slightly with age.
Women
| Age | Healthy | High | Very high |
|---|---|---|---|
| 20–39 | 21–32% | 33–38% | 39%+ |
| 40–59 | 23–33% | 34–39% | 40%+ |
| 60–79 | 24–35% | 36–41% | 42%+ |
Men
| Age | Healthy | High | Very high |
|---|---|---|---|
| 20–39 | 8–19% | 20–24% | 25%+ |
| 40–59 | 11–21% | 22–27% | 28%+ |
| 60–79 | 13–24% | 25–29% | 30%+ |
Below the healthy range (under about 21% for women or 8% for men aged 20–39) is “low”. Very low body fat can disrupt hormones, bone health and, in women, periods. For more on what these ranges mean and where they come from, see what is a healthy body fat percentage? And because where you carry fat matters as much as how much, check your waist-to-height ratio too.
How accurate is a tape-measure body fat test?
For most people, the Navy method lands within a few percentage points of lab methods. It’s far cheaper and easier than a DEXA scan, and more consistent than most bathroom scales. But it has limits:
- Errors grow for people with very high or very low body fat, and for people who carry fat differently from the study groups.
- Military studies have found that tape methods can miss small changes in body composition over a few weeks, so don’t judge progress from a single re-measure.
- The U.S. military itself has moved to updated circumference equations as the science has improved.
The best use is as a trend: measure the same way every 4–6 weeks and watch the direction. A falling waist with a stable weight usually means you’re losing fat and gaining muscle. That’s body recomposition.
How to lower your body fat (without losing muscle)
- Eat in a modest calorie deficit. Find a safe number with our calorie calculator.
- Eat enough protein, around 1.6–2.2 g per kg while dieting. Get your exact target from our protein calculator.
- Lift weights 2–4 times a week, so the weight you lose comes from fat, not muscle. See strength training vs cardio for fat loss.
- Sleep 7+ hours. Short sleep makes fat loss harder (see how sleep affects muscle and fat loss). Check yours with the sleep calculator.
This calculator is for adults and for education only. It isn’t a medical measurement or advice. Read our medical disclaimer, and see all our free health calculators, including the BMI calculator.
Sources
- Hodgdon JA, Beckett MB. Prediction of percent body fat for U.S. Navy men from body circumferences and height (Report No. 84-11) and Prediction of percent body fat for U.S. Navy women from body circumferences and height (Report No. 84-29). San Diego, CA: Naval Health Research Center; 1984.
- Gallagher D, et al. Healthy percentage body fat ranges: an approach for developing guidelines based on body mass index. Am J Clin Nutr. 2000;72(3):694-701. PubMed 10966886
- Deurenberg P, Weststrate JA, Seidell JC. Body mass index as a measure of body fatness: age- and sex-specific prediction formulas. Br J Nutr. 1991;65(2):105-114. PubMed 2043597
- Foulis SA, et al. Body composition changes during 8 weeks of military training are not accurately captured by circumference-based assessments. Front Physiol. 2023;14:1183836. PubMed 37351259
- McClung HL, et al. Science behind policy: implementing a modern circumference-based body fat equation with a physical fitness threshold is associated with lower musculoskeletal injury risk. Int J Obes (Lond). 2025;49(4):723-730. PubMed 40016560
- Taylor KM, et al. Development and cross-validation of a circumference-based predictive equation to estimate body fat in an active population. Obes Sci Pract. 2024;10(2):e747. PubMed 38646612
This article is for informational purposes only and is not medical advice. See our Medical Disclaimer before changing your exercise, diet, or supplement routine.
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Frequently asked questions
How do I calculate my body fat percentage at home?
Use a tape measure and the U.S. Navy method: measure your neck and waist (and hips for women), then enter them with your height into the calculator above. It is typically within a few percentage points of lab methods.
What is a healthy body fat percentage?
For adults aged 20u201339, about 21u201332% for women and 8u201319% for men. Healthy ranges rise slightly with age: up to about 35% for women and 24% for men aged 60u201379.
How accurate is the Navy body fat calculator?
For most people it lands within a few percentage points of lab methods like DEXA or underwater weighing, but errors can be larger at very high or very low body fat. It is most useful for tracking your trend over time with consistent measurements.
Is body fat percentage better than BMI?
Yes, for most purposes. BMI only uses height and weight, so it cannot tell muscle from fat. Body fat percentage, and your waist measurement, say more about health risk.
How do I lower my body fat without losing muscle?
Eat in a modest calorie deficit, get enough protein (about 1.6u20132.2 g per kg), lift weights 2u20134 times a week and sleep 7 or more hours. That combination helps make sure the weight you lose is fat.
What is lean body mass?
Lean body mass is everything in your body that is not fat: muscle, bone, organs and water. It equals your weight minus your fat mass, and the calculator shows both.
Can body fat be too low?
Yes. Very low body fat, roughly under 8% for men or under 20% for women outside of short athletic phases, can disrupt hormones, bone health, immunity and menstrual cycles.