BMI calculator
BMI is weight divided by height squared. It’s quick, but it can’t tell muscle from fat, so add your waist for a better picture.
Short answer
BMI = weight (kg) ÷ height (m)². For adults, 18.5–24.9 is a healthy weight, 25–29.9 overweight and 30 or more obesity (WHO). BMI can’t tell muscle from fat, so check your waist-to-height ratio too.
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BMI categories (WHO, adults)
| BMI | Category |
|---|---|
| Under 18.5 | Underweight |
| 18.5–24.9 | Healthy weight |
| 25–29.9 | Overweight |
| 30–34.9 | Obesity class I |
| 35–39.9 | Obesity class II |
| 40 or more | Obesity class III |
Some health bodies use lower cut-offs for people of South Asian, Chinese, other Asian, Black African and African-Caribbean backgrounds (UK NICE: 23 for overweight, 27.5 for obesity).
BMI vs body fat
A muscular 90 kg lifter at 180 cm has a BMI of 27.8, “overweight”, while being lean. And someone with a “healthy” BMI can carry a lot of body fat with little muscle (often called skinny fat). Waist-to-height ratio and body fat say more. Try the body fat estimator or the waist-to-height ratio calculator.
FAQ
Frequently asked questions
What is a healthy BMI?
18.5 to 24.9 for most adults, by WHO definitions. Your waist and body fat give useful context.
Is BMI accurate for muscular people?
No. BMI counts muscle as weight, so lifters often land in “overweight” while lean.
What’s better than BMI?
Waist-to-height ratio (keep your waist under half your height) and body fat percentage both track health risk and body composition better.