How to use the BMI Calculator
- 1 Choose Metric to enter centimetres and kilograms, or Imperial for feet, inches and pounds.
- 2 Enter your height and your current weight.
- 3 Read your BMI, the category it falls into and where it sits on the colour scale.
- 4 Check the healthy weight range for your height shown under the scale.
Features
WHO adult categories
Results use the World Health Organization adult ranges: under 18.5 underweight, 18.5 to 24.9 healthy, 25 to 29.9 overweight and 30 or more obesity, split into three classes.
Healthy range for your height
The tool turns the healthy BMI range back into kilograms or pounds, which is more useful than the number alone when setting a goal.
Metric and imperial
Switch units at any time. Pounds and inches are converted with exact factors before the calculation.
When to use it
A quick health check
BMI is a simple screening number doctors use alongside other checks. Calculating it at home helps you start a conversation with your doctor.
Tracking progress
If you are changing your diet or activity, recalculate every few weeks to see the trend rather than focusing on one reading.
Before a doctor's visit
Calculate your BMI at home and write it down with your waist measurement, so you and your doctor can talk about the numbers with more context than a single reading.
Frequently asked questions
How is BMI calculated?
BMI is your weight in kilograms divided by your height in metres squared. For 68 kg and 1.70 m, that is 68 divided by 2.89, which is 23.5.
Is BMI accurate for everyone?
No. It does not tell muscle from fat, so very muscular people can show as overweight. It is also less reliable during pregnancy, for older adults and for children, who need age-specific charts.
Are the ranges different for South Asian people?
Some health bodies, following a WHO expert consultation, use lower action points for Asian populations, where health risks rise at a lower BMI, for example from 23 for increased risk. Ask your doctor which ranges apply to you.
Can I use this for children?
No. Children and teenagers need BMI-for-age percentiles, because healthy body fat changes as they grow.
Is this medical advice?
No. BMI is a screening measure only. Speak to a doctor or dietitian before making health decisions.
Is waist size a better measure than BMI?
It adds useful information. Fat around the waist is linked to higher health risks, so doctors often check waist circumference alongside BMI. Measure around your middle at the level of your belly button, after breathing out.
Reviewed by ToolsUnlocked Team · Last updated