What the BMI Calculator does
Body mass index, or BMI, is a simple number that relates your weight to your height. Doctors and health organizations use it as a first check to see whether a person’s weight is in a healthy range for adults. This BMI calculator shows your value, your weight category and the weight range that would count as healthy for your height.
You can enter your height in feet and inches and your weight in pounds, or switch to centimeters and kilograms. A colored scale shows where your result sits between underweight, healthy weight, overweight and obesity, using the categories of the World Health Organization.
BMI is a screening tool, not a diagnosis. It does not measure body fat directly and does not account for muscle mass, age, sex or ethnicity, so it should be seen together with other measurements. Your entries are processed only in your browser and are never stored or sent anywhere.
When to use it
Quick health check
See at a glance whether your weight is in the healthy range for your height.
Setting goals
Find out which weight range would be considered healthy for you before starting a diet or training plan.
Tracking progress
Recalculate after a few weeks to see how your BMI changes over time.
Forms and applications
Some medical, insurance or sports forms ask for your BMI – calculate it in seconds.
Tips for the best results
- Measure your height without shoes and weigh yourself in the morning for the most consistent results.
- Look at your waist size too: a waist over 40 inches (102 cm) for men or 35 inches (88 cm) for women is linked to higher health risks.
- Some health bodies use lower thresholds for people of Asian descent, as health risks can start at a lower BMI.
- Small changes in BMI from day to day are normal and mostly due to water – look at the trend over weeks.
How the BMI Calculator works
BMI equals weight in kilograms divided by height in meters squared. When you use US units, the calculator first converts feet and inches to meters and pounds to kilograms.
The result is then compared with the WHO categories for adults: below 18.5 underweight, 18.5 to 24.9 healthy weight, 25 to 29.9 overweight and 30 or more obesity.
The healthy weight range for your height is found by reversing the formula: 18.5 × height² and 24.9 × height². These values are shown in your chosen unit.