How to use the BMI Calculator
- Choose metric (kg and cm) or imperial (pounds, feet and inches).
- Enter your height and weight.
- Read your BMI, its category on the scale and the healthy weight range for your height.
How BMI is calculated
Body mass index is weight divided by height squared: BMI = kg ÷ m². In imperial units it’s 703 × lb ÷ in². Someone 175 cm tall weighing 72 kg has a BMI of 72 ÷ 1.75² = 23.5.
BMI categories for adults (WHO)
| BMI | Category |
|---|---|
| Below 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 and above | Obesity class III |
What BMI doesn’t tell you
BMI is a quick screening number, not a diagnosis. It doesn’t distinguish muscle from fat, so athletes can score “overweight”, and it doesn’t show where fat is stored. Some health bodies use lower cut-offs for people of Asian descent. For children and teens, BMI is compared with age and sex percentiles instead — this calculator is for adults.
Converting between kilograms and pounds or centimeters and feet? Use the Unit Converter.
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Tools that pair well with the BMI Calculator
- Age Calculator — Enter a date of birth to get the exact age in years, months and days — plus total days and weeks lived, the weekday you were born on, a countdown to the next birthday and your star sign.
- Percentage Calculator — Seven everyday percentage calculations on one page.
- Date Difference Calculator — Count the days between two dates — including business days and a years/months/days breakdown — add or subtract time from a date, or run a live countdown.
- Tip Calculator — Enter the bill, tap a tip percentage and see the tip, the total and what each person pays — with an option to round up so nobody deals with cents.