BMI Calculator
BMI Calculator is a free health tool that runs directly in your browser with no account required.
About this tool
This calculator computes body mass index from your height and weight in either metric (cm/kg) or imperial (in/lb) units and places the result in the standard weight category. BMI is a quick screening ratio, and the result shows the exact figure to one decimal place along with the formula used.
How to use
- Choose your Unit system: cm / kg or in / lb.
- Enter your Height and Weight in those units.
- Read your BMI value and its category from the results.
Frequently asked questions
Which formulas are used?
Metric BMI is weight in kilograms divided by height in meters squared; imperial BMI is weight in pounds divided by height in inches squared, multiplied by 703.
What are the category cutoffs?
The standard adult ranges: under 18.5 is underweight, 18.5 to 24.9 is normal, 25 to 29.9 is overweight, and 30 or above is classed as obesity.
Does BMI apply to everyone?
It is a population-level screening tool that does not distinguish muscle from fat, so athletes, older adults, and children can be misclassified. The adult cutoffs here are not valid for kids, who need age- and sex-specific percentiles.
Why am I getting an error?
Height and weight must both be positive numbers — check that you have not left a field empty or mixed unit systems (for example, entering pounds while metric is selected).
Is my health data stored anywhere?
No. The calculation runs entirely in your browser with nothing saved or transmitted, and the result is informational only — talk to a healthcare provider about what it means for you.