Free, private, for adults
BMI calculator
Enter your height and weight to see your body mass index, your WHO category and a healthy weight range for your height.
Your BMI
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For adults aged 18 and over. BMI is a screening number, not a diagnosis. Calculated in your browser, nothing is sent or saved.
BMI is your weight in kilograms divided by your height in meters squared. For adults, a BMI from 18.5 to 24.9 is in the WHO "healthy weight" range, 25 to 29.9 is overweight and 30 or more is obesity. It is a screening number, not a diagnosis.
Metric and imperial
Use centimeters and kilograms, or feet, inches and pounds. Switch at any time and your numbers are converted for you.
Clear and careful
You see the number, the WHO adult category and a healthy weight range for your height, together with what BMI cannot tell you.
Private
The calculation happens in your browser. Your height and weight are never sent to us or stored.
More tools
Guides
- What is BMIThe formula, its history and what it is for.
- BMI categories chartUnderweight to obesity class 3, in one table.
- Is BMI accurateWhere BMI works and where it misleads.
- BMI for children and teensWhy a different method is used, and why this tool is adult only.
- How our BMI calculator worksThe formula, rounding and privacy, step by step.
A number, not a verdict
BMI is a quick way to compare weight with height. It does not measure body fat, muscle, or how healthy you are, and it can mislead for athletes, older adults and some ethnic groups. Read how accurate BMI is and talk to a doctor about your health.
Frequently asked questions
How is BMI calculated?
BMI equals weight in kilograms divided by height in meters squared. In pounds and inches, multiply weight in pounds by 703 and divide by height in inches squared. For example, 70 kg at 175 cm gives 70 / (1.75 x 1.75) = 22.9.
What is a healthy BMI?
For adults, the WHO defines a healthy weight range as a BMI from 18.5 to 24.9. Below 18.5 is underweight, 25 to 29.9 is overweight, and 30 or more is obesity, divided into classes 1, 2 and 3.
Is BMI accurate?
It is a useful population screening tool but a limited measure for one person. It cannot tell muscle from fat or show where fat is carried. See the guide on accuracy.
Can I use this for children?
No. Children and teenagers are assessed with BMI-for-age percentile charts by a health professional. See BMI for children and teens.
Is my data saved?
No. The calculation runs in your browser. The page only remembers whether you chose metric or imperial units.