BMI Calculator

Enter your weight and height to get your body mass index (BMI), your weight category and the healthy weight range for your height.

How to use the BMI Calculator

  1. Choose metric (kg, cm) or imperial (lb, ft, in) units.
  2. Enter your weight and height.
  3. Read your BMI, its category and the healthy weight range for your height.

How BMI is calculated

BMI = weight (kg) ÷ height (m)²

In imperial units: BMI = 703 × weight (lb) ÷ height (in)². For example, a person who weighs 70 kg and is 1.75 m tall has a BMI of 70 ÷ (1.75 × 1.75) = 22.9.

BMI categories for adults (WHO)

BMI Category
Below 18.5 Underweight
18.5 – 24.9 Healthy weight
25.0 – 29.9 Overweight
30.0 – 34.9 Obesity class I
35.0 – 39.9 Obesity class II
40 and above Obesity class III

Limits of BMI

BMI does not measure body fat directly. Athletes with a lot of muscle can have a high BMI without excess fat, and older adults can have a normal BMI with low muscle mass. It is also not used the same way for children, teenagers or pregnant women. For some Asian populations, health risks rise at a lower BMI, and 23 is often used as the overweight threshold.

This calculator gives general information for healthy adults. It is not medical advice. Talk to a doctor or registered dietitian before making significant changes to your diet or exercise.

Frequently asked questions

What is a healthy BMI?

For most adults a BMI between 18.5 and 24.9 is considered a healthy weight.

How do I calculate BMI by hand?

Divide your weight in kilograms by your height in meters squared. In imperial units, multiply your weight in pounds by 703 and divide by your height in inches squared.

Is BMI accurate for athletes?

Not always. BMI cannot tell muscle from fat, so muscular people may be classed as overweight even with low body fat. A body fat measurement is more useful in that case.

Does BMI apply to children?

Children and teenagers are assessed with age- and sex-specific BMI percentile charts, not the adult categories used here.

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