Check your Body Mass Index in metric or imperial units, and see the healthy weight range for your height.
BMI is a general screening measure, not a diagnosis. It doesn’t account for muscle, body shape or ethnicity. For advice about your health, talk to a doctor.
TL;DR BMI = weight (kg) ÷ height (m)². A BMI of 18.5 to 24.9 is considered a healthy range for adults.
Use this free BMI calculator to check your Body Mass Index in seconds. It works in kilograms and centimetres or pounds and feet, shows which adult BMI category you fall into and gives the healthy weight range for your height.
How to use the BMI calculator
- Choose Metric (kg, cm) or Imperial (lb, ft/in).
- Enter your height and weight.
- Your BMI, category and healthy weight range appear instantly.
How BMI is calculated
BMI = weight in kg ÷ (height in metres)². In imperial units: BMI = 703 × weight in lb ÷ (height in inches)².
Example: 65 kg and 1.70 m tall → 65 ÷ (1.70 × 1.70) = 22.5, which is in the healthy range.
Adult BMI categories (WHO)
| BMI | Category |
|---|---|
| Below 18.5 | Underweight |
| 18.5 – 24.9 | Healthy weight |
| 25.0 – 29.9 | Overweight |
| 30.0 and above | Obesity |
What BMI can and can’t tell you
BMI is a quick screening tool, not a measure of health or fitness. Athletes with lots of muscle can have a “high” BMI while being very fit. It also doesn’t show where fat is stored, and some health organisations use lower cut-offs for people of South Asian, Chinese and other Asian backgrounds. For personal advice, speak to a doctor or healthcare professional.
BMI for students under 18
For children and teenagers, BMI is compared with others of the same age and sex using growth charts (BMI-for-age percentiles). The adult categories above don’t apply, so ask a doctor or school nurse to interpret your result.
Frequently asked questions
What is a healthy BMI?
For most adults, a BMI between 18.5 and 24.9 is considered a healthy range.
Is BMI accurate for athletes?
Not always. BMI doesn't separate muscle from fat, so muscular people can get a high BMI even when they are healthy.
Can I use this BMI calculator if I am under 18?
You can calculate the number, but under-18s are assessed with age- and sex-specific growth charts, so the adult categories don't apply.
Is my data saved?
No. The calculation happens in your browser and nothing you enter is stored or sent anywhere.