In short: BMI is the fastest rough check of whether your weight fits your height. One number, computed the same way worldwide since the 1800s.
Updated August 15, 2026, after a fresh review, with updated visuals and links.
The tool below works in kilograms or pounds, shows your category instantly, and the explanation underneath tells you what the number can and can't say.
Reading your result
The formula is weight divided by height squared: kilograms over meters squared. A 70 kg person at 1.70 m lands at 24.2, inside the healthy window.
The standard bands: under 18.5 is underweight, 18.5 to 24.9 healthy, 25 to 29.9 overweight, 30 and above the obesity range. Athletes with heavy muscle mass often read 'overweight' while being perfectly lean: the formula can't tell muscle from fat.
Use it as a trend tool rather than a verdict: which direction your BMI drifts over months says more than today's value alone.
Worth remembering
- Height slips with age and posture: measure against a wall every so often instead of trusting the number you've carried since high school.
- Pair BMI with a waist measurement for a much sharper picture of health risk than either number alone.
Frequently asked
Is BMI accurate for athletes?
Not particularly: muscle is denser than fat, so muscular people often land in 'overweight' or even 'obesity' ranges while having low body fat. Body composition tests tell that story better.
What is a healthy BMI?
The World Health Organization bands place 18.5 to 24.9 as the healthy range for adults. It's a screening guideline, not a diagnosis.
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