BMI Calculator
BMI Calculator works out your Body Mass Index from your height and weight and tells you which standard category it falls into. Switch between metric (cm/kg) and imperial (in/lb) units with one click.
BMI is a quick, widely used screening figure that estimates whether your weight is in a healthy range for your height.
How to use BMI Calculator
- 1
Pick your units
Choose metric or imperial depending on whether you measure in cm/kg or inches/lb.
- 2
Enter height and weight
Type your height and weight into the two fields.
- 3
Read your BMI
Your BMI and its category appear instantly as you type.
How BMI is calculated
In metric units, BMI is your weight in kilograms divided by the square of your height in metres (kg/m²). In imperial units, it is your weight in pounds divided by the square of your height in inches, multiplied by 703.
For example, someone 1.75 m tall weighing 70 kg has a BMI of 70 / (1.75 × 1.75) ≈ 22.9, which falls in the normal range.
Understanding the categories
The standard adult categories are: below 18.5 is underweight, 18.5 to 24.9 is normal weight, 25 to 29.9 is overweight, and 30 or above is obese.
BMI is a screening tool, not a diagnosis. It does not distinguish muscle from fat and can misclassify very muscular people or older adults. Treat it as one signal and consult a healthcare professional for a full picture.
Frequently asked questions
- What is a healthy BMI?
- For most adults a BMI between 18.5 and 24.9 is considered the healthy range, though individual circumstances vary.
- Does it support pounds and inches?
- Yes. Switch to imperial units to enter height in inches and weight in pounds.
- Is BMI accurate for everyone?
- BMI is a general screening figure and can be misleading for athletes, the elderly and others, because it does not measure body composition directly.
Last updated: