How BMI is calculated
BMI divides your weight by the square of your height. The number is the same whichever units you type in.
| BMI | Category |
|---|---|
| Below 18.5 | Underweight |
| 18.5 – 24.9 | Normal |
| 25 – 29.9 | Overweight |
| 30 and above | Obese |
Common questions
What's BMI Prime?
It's your BMI divided by 25 (the top of the normal range), shown as a ratio — 1.0 means you're right at the upper edge of normal. It's the same information as your category, just as one number instead of a label.
Does BMI account for muscle mass?
No — it only uses height and weight, so a muscular person with low body fat can land in "overweight" or "obese" purely from muscle mass. If that might be you, the body fat calculator is a better read on where you actually stand.
What happens above a BMI of 40?
It still shows as "Obese" — this calculator doesn't split obesity into further classes (some clinical scales go to Class III at 40+). The category label is the same either way; only the exact number changes.
For general information only — not medical advice. Talk to a doctor about anything that concerns you.