BMI Calculator
Calculate your body mass index (BMI) from your weight and height, see your weight category and find the healthy weight range for your height. Use metric or imperial units.
For adults aged 20 and over. BMI is a screening number, not a medical diagnosis, and it is not suitable for children, teenagers or pregnancy. Talk to a doctor for personal health advice.
How to use the BMI Calculator
- Choose metric (kilograms and centimeters) or imperial (pounds, feet and inches).
- Enter your weight and height. The result updates as you type.
- Read your BMI, your category on the scale, and the weight range that falls within a healthy BMI for your height.
BMI categories for adults
These are the standard adult categories used by the World Health Organization and many health services:
| BMI | Category |
|---|---|
| Below 18.5 | Underweight |
| 18.5 to 24.9 | Healthy weight |
| 25.0 to 29.9 | Overweight |
| 30.0 and above | Obesity |
How BMI is calculated
BMI is your weight in kilograms divided by your height in meters squared. With imperial units the formula is 703 × weight in pounds ÷ height in inches squared.
Example (metric): a person who weighs 70 kg and is 170 cm (1.70 m) tall has a BMI of 70 ÷ (1.70 × 1.70) = 70 ÷ 2.89 = 24.2, which is in the healthy weight range.
Example (imperial): 154 lb at 5 ft 7 in (67 in) gives 703 × 154 ÷ 67² = 24.1.
Limits of BMI
BMI is a quick screening tool, not a measure of health on its own. It does not measure body fat or show where fat is stored, and it cannot tell muscle from fat, so very muscular people can have a high BMI without excess body fat. It can also be less accurate for older adults. Some guidelines use lower cutoffs for people of South and East Asian descent, because health risks can appear at a lower BMI. For children and teenagers, BMI is compared with growth charts for their age and sex instead of the adult categories above.
Doctors usually look at BMI together with other measures such as waist size, blood pressure, blood tests and family history.
Frequently asked questions
What is a healthy BMI?
For adults, a BMI from 18.5 to 24.9 is classed as a healthy weight. The calculator also shows the weight range that matches this BMI for your height.
Is BMI a medical diagnosis?
No. BMI is a general screening number. It can point to possible weight-related health risks, but only a doctor can assess your health.
Is BMI accurate for athletes and muscular people?
Not always. Muscle weighs more than fat, so a very muscular person can have a high BMI without excess body fat. Other measures, such as waist size or body fat percentage, can give a fuller picture.
Can I use this BMI calculator for children?
No. This calculator uses adult categories. A child's BMI is compared with growth charts for their age and sex, so ask a pediatrician or use a BMI-for-age tool.
How do I convert pounds and feet for BMI?
Switch the units to imperial and enter pounds, feet and inches. The calculator converts them for you with the standard factors: 1 lb = 0.45359 kg and 1 in = 2.54 cm.
Is my data stored or uploaded?
No. The calculator is free and everything runs in your browser. Your weight and height are never uploaded to a server or stored.