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BMI Calculator
Work out your body mass index in metric or US units, see which category it falls in, and find the healthy weight range for your height.
How it works
Body mass index is your weight in kilograms divided by your height in metres squared: BMI = kg ÷ m². If you use pounds and inches, the calculator converts them first (1 lb = 0.4536 kg, 1 inch = 2.54 cm), so the answer is the same in either unit system.
The healthy weight range shown under your result is the weight that would give a BMI between 18.5 and 24.9 at your height.
BMI categories for adults
- Below 18.5: underweight
- 18.5 to 24.9: healthy weight
- 25 to 29.9: overweight
- 30 and above: obese
These are the World Health Organization ranges used by most doctors. Some health services use lower cut-offs for people of South Asian, Chinese and other Asian backgrounds, because health risks can rise at a lower BMI.
Worked example
Someone who weighs 70 kg and is 175 cm tall has a height of 1.75 m. 1.75 × 1.75 = 3.0625, and 70 ÷ 3.0625 = 22.9. That is in the healthy range. For the same height, a healthy weight is roughly 56.7 kg to 76.3 kg.
What BMI does not tell you
- It does not separate muscle from fat, so athletes and very muscular people can score as overweight.
- It does not show where fat is stored. Waist size is a useful second check: a waist over half your height is a common warning sign.
- It is not designed for children, teenagers or pregnant women, who need age- or stage-specific charts.
Frequently asked questions
What is a healthy BMI?
For most adults a BMI from 18.5 to 24.9 is considered healthy.
Is BMI accurate?
It is a quick screening tool that works well for groups of people, but it cannot tell muscle from fat, so use it alongside waist size and advice from a doctor.
Can I use this BMI calculator for children?
No. Children and teenagers need BMI-for-age percentile charts because their bodies change as they grow.
Does BMI differ for men and women?
The formula and adult categories are the same for both, although women naturally tend to carry more body fat at the same BMI.
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