BMI Calculator
Enter your height and weight to find your body mass index (BMI), your weight category and the healthy weight range for your height. This calculator is for adults aged 18 and over.
BMI is a general screening measure, not a diagnosis. It does not replace advice from a doctor. Read our Terms and Disclaimer.
How it works
BMI compares your weight with your height. The calculator converts imperial units to metric, works out BMI, and rounds it to 1 decimal place. The category is based on the rounded value.
Formula
BMI = weight in kg ÷ (height in metres × height in metres)
Imperial units are converted first: 1 inch = 2.54 cm and 1 lb = 0.45359237 kg. The healthy weight range is the weight that gives a BMI of 18.5 to 24.9 at your height.
BMI categories for adults
| BMI | Category |
|---|---|
| Below 18.5 | Underweight |
| 18.5 to 24.9 | Normal weight |
| 25.0 to 29.9 | Overweight |
| 30.0 and above | Obese |
These are the standard adult categories used by the World Health Organization.
Steps
- Choose metric or imperial units.
- Type your height and weight.
- Press Calculate BMI and read your BMI, category and healthy weight range.
Examples
- 70 kg and 175 cm: 70 ÷ (1.75 × 1.75) = 22.9, normal weight
- 154 lb and 5 ft 9 in: about 69.9 kg and 175.3 cm gives 22.7, normal weight
- 80 kg and 170 cm: 27.7, overweight
Common uses
A quick check of where your weight sits for your height, tracking change over time, and having a starting point for a conversation with your doctor or dietitian.
Frequently asked questions
Is BMI accurate?
BMI is a simple estimate. It does not measure body fat, muscle, bone or where fat is stored. Athletes and people with a lot of muscle can have a high BMI without carrying extra fat, and older adults can have a normal BMI with little muscle.
Does BMI work for children, teenagers or pregnancy?
No. Children and teenagers are assessed against charts for their age and sex, and BMI is not a reliable guide during pregnancy. Ask a doctor in these cases.
Are the cut-offs different for South Asian people?
Some health bodies suggest lower cut-offs for South Asian and some other Asian populations, with health risk rising from a BMI of around 23. This calculator shows the standard categories above. A doctor can tell you which target suits you.
Why does it ask for height between 50 and 250 cm?
This range covers all adult heights, and it helps catch typing mistakes such as a missing digit. Weight must be between 10 and 500 kg.