Body fat calculator
Enter your sex, age, height, weight and your neck and waist measurements (plus your hip, if you're a woman): we'll show you your body fat percentage, your fat and lean mass, and whether you're in the healthy range for your age.
It's a tape measure estimate, not a measurement. It doesn't replace a professional. It doesn't apply during pregnancy or to anyone under 18.
Take it to your plan. Mobbe builds your routine and works out your calories and protein to lose fat while keeping muscle; with PRO, your meals too.
How to measure yourself
With a flexible tape measure, standing up, relaxed and without sucking in your stomach.
- NeckJust below the Adam's apple (the larynx), with the tape sloping slightly forward.
- WaistMen, at the navel. Women, at the narrowest point.
- HipWomen only: at the widest point of the glutes.
Keep the tape snug without pressing into the skin. Measure twice and use the average, in the morning before eating.
Healthy body fat percentage by age
Ranges for adults from Gallagher et al. (2000). At 18 and 19, use the 20 to 39 row.
| Age | Low | Healthy | High | Very high |
|---|---|---|---|---|
| 20–39 years | <21 | 21–32.9 | 33–38.9 | ≥39 |
| 40–59 years | <23 | 23–33.9 | 34–39.9 | ≥40 |
| 60–79 years | <24 | 24–35.9 | 36–41.9 | ≥42 |
| Age | Low | Healthy | High | Very high |
|---|---|---|---|---|
| 20–39 years | <8 | 8–19.9 | 20–24.9 | ≥25 |
| 40–59 years | <11 | 11–21.9 | 22–27.9 | ≥28 |
| 60–79 years | <13 | 13–24.9 | 25–29.9 | ≥30 |
How body fat percentage is calculated
The US Navy formula and the ranges by age, with the worked example.
- Step 1
The US Navy formula
It uses your height and the difference between your waist and neck, in centimeters. A man at 178 cm (5 ft 10 in) with an 88 cm waist and a 39 cm neck: 18.0%. At 82 kg, that's 14.7 kg of fat mass and 67.3 kg of lean mass. In inches (34.6 in waist, 15.4 in neck, 181 lb) it gives 17.8%, because the measurements are rounded. For women it uses waist + hip − neck and the numbers change: 1.29579, 0.35004 and 0.221.
men: % = 495 / (1.0324 − 0.19077 × log(waist − neck) + 0.15456 × log(height)) − 450Hodgdon and Beckett, 1984. - Step 2
Healthy range by age and sex
The cutoffs come from a study that compared measured body fat with BMI in adults. From 20 to 39, healthy is 8% to 19.9% for men and 21% to 32.9% for women. At 18 and 19 that row applies; at 80, the 60 to 79 row.
Gallagher et al., 2000. - Step 3
How accurate it is
Compared with underwater weighing, the typical error is 3 to 4 points: if you get 18.0%, your real value may be a few points higher or lower. Treat it as a reference, not an exact number.
Hodgdon and Friedl, 1999. - Step 4
How Mobbe uses it
With your goal, Mobbe works out your calories and protein to lose fat while keeping muscle, and reviews adjust the plan with your real weight.
Helms, 2014; Garthe, 2011.
Sources
- Hodgdon JA, Beckett MB. Prediction of percent body fat for U.S. Navy men from body circumferences and height. Report No. 84-11. San Diego, CA: Naval Health Research Center; 1984.
- Hodgdon JA, Beckett MB. 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, Heymsfield SB, Heo M, Jebb SA, Murgatroyd PR, Sakamoto Y. Healthy percentage body fat ranges: an approach for developing guidelines based on body mass index. Am J Clin Nutr. 2000;72(3):694-701. doi:10.1093/ajcn/72.3.694
- Hodgdon JA, Friedl KE. Development of the DoD body composition estimation equations. Technical Report No. 99-2B. San Diego, CA: Naval Health Research Center; 1999.
- Kyle UG, Bosaeus I, De Lorenzo AD, et al. Bioelectrical impedance analysis—part I: review of principles and methods. Clin Nutr. 2004;23(5):1226-1243. doi:10.1016/j.clnu.2004.06.004
- Helms ER, Zinn C, Rowlands DS, Brown SR. A systematic review of dietary protein during caloric restriction in resistance trained lean athletes: a case for higher intakes. Int J Sport Nutr Exerc Metab. 2014;24(2):127-138. doi:10.1123/ijsnem.2013-0054
- Garthe I, Raastad T, Refsnes PE, Koivisto A, Sundgot-Borgen J. Effect of two different weight-loss rates on body composition and strength and power-related performance in elite athletes. Int J Sport Nutr Exerc Metab. 2011;21(2):97-104. doi:10.1123/ijsnem.21.2.97
Frequently asked questions
What body fat percentage is healthy?
It depends on age and sex. From 20 to 39, 21% to 32.9% for women and 8% to 19.9% for men. The range goes up a few points with age.
How accurate is this calculator?
It's a tape measure estimate: compared with underwater weighing, the typical error is 3 to 4 points. Always measure the same way: same spot, same time of day and the tape without pressing.
What about bioimpedance scales?
They send a weak electric current through your body and estimate fat from how hard it is for it to pass. Since water conducts the current, how much you drank, whether you trained or whether you ate all change the reading. To compare, use the same scale at the same time of day.
What's the difference from BMI?
BMI only uses your weight and height, so it can't tell muscle from fat. Body fat percentage estimates how much of your weight is fat. Calculate your BMI.
How do I lose fat without losing muscle?
With a moderate deficit, enough protein and strength training. Losing weight slowly helps you keep more muscle. Read the body recomposition guide.
Guides to get more out of it
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Mobbe builds your plan with these numbers
Download Mobbe and answer a few questions: with your goal it works out your calories and protein to lose fat without losing muscle, builds your routine and, with PRO, your meal plan.
