Body Mass Index — a quick estimate of how your weight relates to your height. Not a medical diagnosis.
| Underweight | BMI < 18.5 |
| Normal | 18.5–24.9 |
| Overweight | 25–29.9 |
| Obese | ≥ 30 |
This free BMI calculator estimates your Body Mass Index from your height and weight. Enter both (metric or imperial) and it instantly returns your BMI number and the category it falls in. Use it as a rough screening number — not a diagnosis. It runs in your browser; nothing is saved and there's no sign-up.
For most adults a BMI of 18.5–24.9 is classed as the “normal” range, 25–29.9 as overweight, and 30+ as obese, with under 18.5 considered underweight. These are population-level bands, not a verdict on any individual — muscle, age and build all shift what's healthy for you.
Not very. BMI only knows height and weight, so it can't tell muscle from fat — a lean, muscular person can read as “overweight” despite low body fat. For athletes, measures like body-fat percentage or waist-to-height ratio tell a truer story.
Weight in kilograms divided by height in metres squared (kg ÷ m²). In imperial it's weight in pounds × 703, divided by height in inches squared. This tool just does that math for you and labels the result.
The adult ranges are the same for men and women, but BMI is interpreted differently for children and teens, who are scored against age-and-sex percentiles rather than the fixed adult bands. If you're checking a child, use a pediatric BMI-for-age chart.
It's a quick, free screening tool, not a health checkup. It says nothing about blood pressure, blood sugar, fitness or where fat sits on your body — all of which matter more. Treat a high or low number as a prompt to look closer, ideally with a doctor.