On this page
Muscle vs. BMI
Two people can have the same height, weight and BMI with very different bodies. Move the sliders, or try the presets:
Who BMI misclassifies
BMI tends to overestimate body fat in:
- Strength and power athletes: rugby, American football, weightlifting, sprinting, rowing.
- Bodybuilders and people who lift regularly.
- Athletes with large frames.
It's usually accurate enough for endurance athletes such as distance runners, who carry less muscle mass relative to height.
Better ways to check body composition
| Method | What it measures | Notes |
|---|---|---|
| Waist size | Fat around the stomach | Free. Under 40 in (men) or 35 in (women) is lower risk1 |
| Waist-to-height ratio | Waist relative to height | Free. Under 0.5 is the common target |
| Skinfold calipers | Fat under the skin at several sites | Cheap, but accuracy depends on the person measuring |
| Bioelectrical impedance (smart scales) | Body fat from electrical resistance | Convenient, but affected by hydration |
| DEXA scan | Fat, muscle and bone separately | Very accurate, but costs money |
How the calculation works
Here is the exact math behind your result, using your own numbers.
Frequently asked questions
Is BMI accurate for athletes?
Not for muscular athletes. It's a weight-for-height measure, so extra muscle raises it just like extra fat. Use waist size or a body-fat measurement as well.
What's a good body fat percentage for an athlete?
The American Council on Exercise lists about 6–13% for men and 14–20% for women in its "athletes" range.2 Healthy ranges depend on the sport.
Sources
Further reading
This page is for education and is not medical advice. Talk with a healthcare professional about your weight and health.
