Free BMI calculator

Body Mass Index (BMI) estimates whether your weight is healthy for your height. Enter height in cm and weight in kg to get your BMI and category. Under 18.5 is underweight, 18.5–24.9 normal, 25–29.9 overweight, 30+ obese.

How to use the BMI calculator

Enter your weight in kilograms.
Enter your height in centimetres.
Click Calculate to see your BMI and its category.

How BMI is calculated

Body Mass Index (BMI) estimates whether your weight is in a healthy range for your height. It's your weight in kilograms divided by the square of your height in metres:

BMI = weight (kg) ÷ height (m)²

Worked example

Someone weighing 70 kg at 1.75 m has a BMI of 70 ÷ (1.75 × 1.75) = 22.9, which falls in the "normal weight" range.

BMI categories (WHO)

BMI range	Category
Below 18.5	Underweight
18.5 – 24.9	Normal weight
25.0 – 29.9	Overweight
30.0 and above	Obese

What BMI doesn't tell you

It doesn't distinguish muscle from fat — athletes can read as "overweight" despite low body fat.
It doesn't account for fat distribution, age or ethnicity.
Use it as a quick screening tool, not a diagnosis — pair it with waist measurement and a doctor's advice.

Frequently asked questions

How is BMI calculated?

BMI = weight (kg) ÷ height (m)². This tool does it for you from cm and kg.

What is a healthy BMI?

A BMI between 18.5 and 24.9 is generally considered healthy for adults.

BMI Calculator