BMI Calculator
Work out your BMI (body mass index) in seconds, in metric or imperial, with a clear guide to the healthy range for adults. Nothing is stored, and it stays in your browser.
Enter your height and weight
BMI is a general guide for adults only, not a diagnosis. It does not apply to children, and it does not account for muscle, body shape or pregnancy. If you have any concerns about your weight or health, your GP is the best person to talk to.
How it works
- 1
Pick your units
Switch between metric (kg and cm) and imperial (stones, pounds, feet and inches).
- 2
Enter your details
Pop in your height and weight and your BMI updates instantly.
- 3
See the range
We show your number against the healthy adult range, with context on what it means.
Common questions
What is a healthy BMI?
For most adults, a BMI between 18.5 and 24.9 is considered a healthy weight, 25 to 29.9 is overweight, and 30 or above is obese. Below 18.5 is underweight.
How is BMI calculated?
BMI is your weight in kilograms divided by the square of your height in metres. This tool does the maths for you in whichever units you prefer.
Can I use this for my child?
No. For children and teenagers, BMI is read against age and sex growth charts (centiles), not the adult categories here. Please speak to your GP or health visitor for a child's BMI.
Is BMI accurate?
It's a useful general guide but a blunt one: it doesn't account for muscle, body shape, or pregnancy. Treat it as one small piece of the picture, alongside how you feel and advice from your GP.