How to calculate your BMI
- Choose metric (centimetres and kilograms) or US units (feet, inches and pounds).
- Enter your height and weight. Your BMI, its category and a gauge appear instantly.
- Check the healthy weight range for your height. Tick Asian cut-offs if you are of Asian descent, as recommended by the WHO expert consultation.
- Use Copy link to save or send the result; the link restores your numbers.
The BMI formula and categories
Body mass index is weight in kilograms divided by height in metres squared: BMI = kg ÷ m². In US units, BMI = 703 × lb ÷ in². For example, 70 kg at 1.75 m gives 70 ÷ 3.0625 = 22.9. The World Health Organization's adult categories are: under 18.5 underweight, 18.5–24.9 healthy weight, 25–29.9 overweight, 30–34.9 obesity class I, 35–39.9 class II, and 40 or more class III. Because people of Asian descent tend to have higher health risks at lower BMI, many Asian health authorities use 23 and 27.5 as the overweight and obesity thresholds.
Limits of BMI
BMI is quick and useful for populations, but it does not distinguish muscle from fat or show where fat is stored. Athletes can have a high BMI with little body fat, and older adults can have a normal BMI with low muscle mass. It is not valid for children and teenagers (who are assessed with age- and sex-specific percentiles) or during pregnancy. Waist circumference (a waist-to-height ratio below 0.5) adds useful information. This calculator gives an estimate, not medical advice; your numbers stay in your browser.
What is a healthy BMI?
For most adults, 18.5 to 24.9. For people of Asian descent, 18.5 to 22.9 is often recommended.
Is BMI accurate for muscular people?
No. Muscle is dense, so muscular people may be classed as overweight while having low body fat. Body fat or waist measurements are more informative.
Can children use this BMI calculator?
No. Children's BMI must be compared with growth charts for their age and sex. Ask your doctor or use a pediatric BMI percentile tool.
What is BMI Prime?
Your BMI divided by 25, the upper limit of the healthy range. A value above 1.0 means above the healthy range.