BMI Calculator
Calculate BMI
Enter your height and weight to calculate your BMI. You can switch between imperial (ft, in, lb) and metric (cm, kg) units. The result shows your BMI, your weight category according to the World Health Organization (WHO), the healthy weight range for your height and how far you are from it.
What is BMI?
BMI (Body Mass Index) is a simple screening measure that relates your weight to your height. It is widely used to check whether an adult is underweight, at a healthy weight, overweight or living with obesity.
BMI formula
Metric: BMI = (w: weight in kilograms, h: height in meters)
Imperial: BMI = (w: weight in pounds, h: height in inches)
BMI chart for adults (WHO)
For adults aged 18 and over:
| Category | BMI |
|---|---|
| Underweight | BMI < 18.5 |
| Normal weight | 18.5 ≤ BMI < 25 |
| Overweight | 25 ≤ BMI < 30 |
| Obesity (Class I) | 30 ≤ BMI < 35 |
| Obesity (Class II) | 35 ≤ BMI < 40 |
| Obesity (Class III) | BMI ≥ 40 |
A healthy BMI for adults is between 18.5 and 24.9. A BMI of 25 or more is overweight, and 30 or more is obesity.
Waist size matters too: a waist of 94 cm (37 in) or more for men, or 80 cm (31.5 in) or more for women, indicates abdominal obesity and a higher risk of heart disease and type 2 diabetes.
BMI for children and teens (5–17 years)
Children and teens are still growing, so the adult chart does not apply. Tick “Under 18”, then enter sex and age (years and months). The calculator uses the WHO 2007 Growth Reference (BMI-for-age, 5–19 years): above +1 SD is overweight, above +2 SD is obesity and below −2 SD is thinness. The reference values for that age and sex are shown below the result.
Limitations of BMI
BMI does not measure body fat directly. Muscular people and athletes can have a high BMI without excess fat, while older adults may have more body fat at the same BMI. Use BMI together with waist size and, if needed, a check-up with a health professional.
Frequently asked questions
What is a healthy BMI?
For adults, a BMI from 18.5 to 24.9 is considered a healthy weight by the WHO.
How do I calculate BMI in pounds and inches?
Multiply your weight in pounds by 703, then divide by your height in inches squared. For example, 160 lb and 5 ft 9 in (69 in): 160 × 703 ÷ 69² ≈ 23.6.
Is BMI the same for men and women?
Yes, the adult BMI categories are the same for men and women. For children and teens, sex and age are taken into account.
Is BMI accurate for athletes?
Not always. Because muscle is heavier than fat, very muscular people can be classified as overweight even when their body fat is low.
Standards and sources
Adult categories follow the WHO BMI classification; waist thresholds follow the WHO expert consultation and the International Diabetes Federation (IDF) for European populations.