Calculate your muscle mass percentage
Enter your sex, age, height and weight and get your estimated skeletal muscle mass, in kilos and as a percentage, with its margin of error. We then compare it with the average measured by MRI, which is the real reference, not a bathroom scale.
Estimated using the Lee et al. (2000) equation, validated against MRI in adults. Not a diagnosis.
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How is muscle mass calculated?
We use the Lee et al. equation (American Journal of Clinical Nutrition, 2000), developed by measuring muscle with whole-body MRI and needing only weight, height, age and sex: muscle (kg) = 0.244 × weight + 7.80 × height in metres + 6.6 if male − 0.098 × age − 3.3. It explains 86% of the differences between people and is off by about 2.8 kg on average, which is why you get the result with its margin. It was validated in adults with a BMI under 30; above that the number is only a rough guide. The original equation also adjusts by 1 to 1.5 kg for ethnicity; here we use the study’s reference group. We compare it with Janssen et al. (2000), who measured 468 adults aged 18 to 88 by MRI: 38.4% muscle in men and 30.6% in women on average.
Estimated muscle mass by profile and age
A few example profiles using the same equation as the calculator. Two things stand out: at the same weight and height the percentage drops with age, and between sexes the gap is several points. As an MRI-measured reference: 38.4% on average in men and 30.6% in women (Janssen 2000).
| Profile | Age 25 | Age 45 | Age 65 |
|---|---|---|---|
| Woman · 160 cm · 58 kg | 36.0 % (20.9 kg) | 32.6 % (18.9 kg) | 29.2 % (17.0 kg) |
| Woman · 168 cm · 68 kg | 35.2 % (23.9 kg) | 32.3 % (22.0 kg) | 29.4 % (20.0 kg) |
| Man · 175 cm · 75 kg | 43.7 % (32.8 kg) | 41.1 % (30.8 kg) | 38.5 % (28.9 kg) |
| Man · 182 cm · 88 kg | 41.5 % (36.5 kg) | 39.3 % (34.6 kg) | 37.0 % (32.6 kg) |
Skeletal muscle estimated with model 2 of Lee et al. (Am J Clin Nutr, 2000), validated against MRI in adults with a BMI under 30; margin of ±2.8 kg. Not the same as the lean mass a bioimpedance scale reports. These are reference ranges for healthy adults, not a diagnosis or individual advice.
FAQ
What muscle mass percentage is normal?
Measured by MRI, men carry on average 38.4% of their body weight as skeletal muscle and women 30.6% (Janssen et al., 2000, 468 adults aged 18 to 88). These are population averages, not an ideal: weight and height alone explain half of the differences between people.
Why does my scale show a higher percentage?
Because most bioimpedance scales report lean or fat-free mass, which includes muscle, bone, organs and water. Skeletal muscle is only part of that, so its number comes out quite a bit lower. Always compare readings from the same device.
Does muscle mass drop with age?
Yes. In the reference study the percentage starts falling as early as the third decade, although the kilos of muscle do not drop noticeably until after 50, mostly in the legs. That is why the calculator asks for your age.
How can I build muscle mass?
What matters most is regular strength training and eating enough protein spread across the day. If you want a protein number, the protein calculator gives you one for your weight and goal.
Keep reading
- Muscle mass percentage: what is normal for your age and sex →
- How much protein do you need →
- How many calories should I eat a day →
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