BMI Calculator
Enter height and weight for a Body Mass Index score and category. This is a simple screening figure, not a diagnosis.
Or enter pounds only in the lb box and leave stones at 0.
Your BMI is 0
Adult BMI bands follow the usual WHO cut-offs. They do not account for muscle mass, pregnancy, ethnicity or age. Speak to a clinician if you need advice about your weight.
How to use the BMI Calculator
- Choose Metric (cm and kg) or Imperial (feet, inches, stones and pounds).
- Enter height and weight. On imperial, you can leave stones at 0 and put the full weight in pounds.
- The BMI score and category update as you type. Use Calculate BMI if you want to force a refresh, or Clear to empty the fields.
- Read the healthy weight range under the scale. That band is for the height you entered, not a target for everyone.
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What it is for
Body Mass Index is weight in kilograms divided by height in metres squared. Health services use the resulting number as a quick screen, not as a full picture of health. This page does that arithmetic and places the score on the usual adult bands.
Under 18.5 is classed as underweight, 18.5 to 24.9 as a healthy weight, 25 to 29.9 as overweight, and 30 and above as obesity (split into classes I, II and III). Those cut-offs come from the World Health Organization’s adult ranges. They are not designed for children, and they do not adjust for muscle mass, pregnancy, bone density, ethnicity or where fat sits on the body.
Use it to see where a figure lands, or to check the healthy weight window for a given height. It will not tell you whether you should lose or gain weight. For that, speak to a GP or another qualified clinician. Related calculators on Catpool include the Calculators hub.
Why it runs in your browser
Height and weight stay in the tab. Nothing is sent to Catpool and you do not create an account. Close the page and the numbers are gone.
Common questions
Which units should I use?
Metric if you think in centimetres and kilograms. Imperial if you think in feet, inches, stones and pounds. The BMI number is the same either way.
Why is my BMI “overweight” when I lift weights?
BMI treats extra mass as extra fat. Muscle is heavy, so a trained person can sit in the overweight band and still be fine. That is a known limit of the measure, not a fault in the calculator.
Does it work for children?
No. Child and teen BMI is read against age-and-sex charts, not these adult cut-offs. Ask a health visitor or GP for that reading.
Is the healthy range a goal I should hit?
It is the weight band that corresponds to BMI 18.5–24.9 at your height. It is a reference, not a prescription.
Is this medical advice?
No. It is an arithmetic tool. If you are worried about your weight, eating or health, use an NHS or clinician service rather than a webpage.
Related: Calculators, Age Calculator, About.
