BMI Calculator
BMI is weight divided by height squared. It is a useful population screening tool and a poor individual one, because it cannot distinguish muscle from fat.
Your results
BMI takes no account of muscle mass, bone density or fat distribution, so it routinely classifies muscular people as overweight. Waist-to-height ratio is a better single number.
What BMI is for
BMI was devised for population statistics, and at that job it works — across large groups it correlates with health outcomes well enough to be useful.
Applied to one person it is much weaker. A 100 kg muscular lifter at 180 cm has a BMI of 30.9, categorised as obese. A sedentary person of the same height and weight with far more fat gets the identical number. The measure cannot tell them apart.
Better single measures
- Waist-to-height ratio. Keep your waist under half your height. Better correlated with metabolic risk than BMI and just as easy to measure — see the waist-to-height calculator.
- Waist circumference alone. The single best fat-loss tracking measure.
- FFMI if you lift, since it accounts for lean mass — see the FFMI calculator.
Common questions
Is BMI accurate?
For populations, reasonably. For an individual — particularly a muscular one — it is a crude proxy.
What is a healthy BMI?
18.5–24.9 is the standard normal range, with 25–29.9 classed as overweight and 30+ as obese. Thresholds differ for some ethnic groups.
Why is my BMI high when I am lean?
Muscle is dense. BMI counts it as weight and draws no distinction.
What should I use instead?
Waist-to-height ratio, waist circumference, and photographs over time.
Related calculators
Track the numbers, not just calculate them
MyFitsy stores your weight, measurements and every session, so the figures above become a trend instead of a one-off.
