BMI Calculator - Calculate Your Body Mass Index

Units

Adult BMI classification (WHO)

  • Below 18.5: underweight
  • 18.5 to 24.9: normal weight
  • 25 to 29.9: overweight
  • 30 to 34.9: obesity class I
  • 35 to 39.9: obesity class II
  • 40 and above: obesity class III

BMI is an indicator designed for adults. It does not apply in the same way to children and teenagers, pregnant women or very muscular people, and it does not replace advice from a health professional.

How to use this calculator?

1. Choose your units: metric or imperial
2. Enter your weight and height
3. Read your BMI, its category and the weight range that matches a normal BMI

Quick answer

How do you calculate your BMI?

Divide your weight in kilograms by the square of your height in metres: BMI = weight ÷ height². Example: 70 kg at 1.75 m gives 70 ÷ (1.75 × 1.75) = 22.9, which is a normal weight according to the WHO (between 18.5 and 24.9). This classification applies to adults.

BMICategory (WHO, adults)
Below 18.5Underweight
18.5 to 24.9Normal weight
25 to 29.9Overweight
30 to 34.9Obesity class I
35 to 39.9Obesity class II
40 and aboveObesity class III

About the BMI Calculator

What is it?

The BMI (body mass index) calculator relates your weight to your height. It shows your BMI to one decimal place, the matching category in the World Health Organization (WHO) classification and the weight range that corresponds to a normal BMI for your height.

Why use it?

BMI is a simple, widely used reference for assessing body weight in adults. It is only one indicator: it does not tell muscle from fat, does not apply in the same way to children, pregnant women or very muscular people, and does not replace medical advice.

How does it work?

Formula: BMI = weight (kg) ÷ height² (m). For example, 70 kg at 1.75 m gives 70 ÷ (1.75 × 1.75) = 22.9. With imperial units, weight is converted to kilograms (1 lb = 0.4536 kg) and height to meters (1 inch = 2.54 cm). The healthy weight range is 18.5 × height² to 24.9 × height².

Usage tips

  • Weigh yourself preferably in the morning, under similar conditions each time
  • For children and teenagers, BMI is read against growth charts by age and sex
  • Waist circumference is a useful complement to BMI to assess fat distribution
  • Track how your BMI changes over time rather than focusing on a single value
  • If you have doubts about your weight or health, talk to a health professional
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