BMI Calculator
Check your Body Mass Index in seconds
Free Online BMI Calculator
Body Mass Index for metric and imperial units
Your Body Mass Index (BMI) is a quick way to see whether your weight is in a healthy range for your height. Enter your height and weight in metric or imperial units and this calculator instantly shows your BMI, the category it falls into, and the healthy weight range for your height. Results update as you type and everything is calculated privately in your browser.
Features
Metric & Imperial
Enter centimetres and kilograms or feet, inches and pounds.
Instant Category
See at a glance whether you are underweight, normal, overweight or obese.
Healthy Range
Get the ideal weight range for your specific height.
Private & Free
No account, no tracking of your body data. Calculated on your device.
WHO Categories & Formula
WHO BMI categories (adults)
- Below 18.5 — Underweight
- 18.5 – 24.9 — Normal weight
- 25 – 29.9 — Overweight
- 30 – 34.9 — Obesity (Class 1)
- 35 and above — Obesity (Class 2-3)
The formula
- BMI = weight (kg) ÷ height² (m²)
- Example: 70 kg, 1.75 m → 70 ÷ 3.06 ≈ 22.9
- Imperial: 703 × pounds ÷ inches²
- For adults; children use percentile charts
Frequently Asked Questions
How is BMI calculated?
BMI equals your weight in kilograms divided by the square of your height in metres. For imperial units, BMI is 703 times weight in pounds divided by height in inches squared.
What is a healthy BMI?
A BMI between 18.5 and 24.9 is generally considered a healthy weight for most adults.
Should BMI be different for men and women?
For adults the BMI formula and its categories are the same for both sexes. What differs is body composition (muscle versus fat), which BMI does not measure. To account for that, a body fat percentage calculation is more informative than BMI alone.
Is BMI accurate for everyone?
BMI is a useful general guide but it does not account for muscle mass, body composition, age or sex. Athletes and some groups may get misleading results, so treat it as one indicator among many.
Does the calculator store my data?
No. Your height and weight are processed entirely in your browser and are not sent anywhere.
Does BMI apply to children?
No. For ages 2-18, BMI is assessed with age- and sex-specific percentile charts; this tool is designed for adults.