How to Calculate BMI Online
Calculate body mass index with metric or imperial measurements and understand what the result means.
On this page
Quick answer
Choose metric or imperial units, enter your height and weight, and calculate. Kivrum divides weight by height squared and displays your BMI with its standard adult category.
What BMI measures
Body mass index compares weight with height. The metric formula is weight in kilograms divided by height in meters squared. The imperial calculation uses pounds and inches with a conversion factor.
BMI is a general screening estimate, not a diagnosis. It does not directly measure body fat, muscle mass, fitness, or overall health.
How to calculate BMI
The calculator supports both common unit systems.
- 1
Choose your units
Select metric for kilograms and centimeters or imperial for pounds, feet, and inches.
- 2
Enter height and weight
Use current, accurate measurements and check the selected units.
- 3
Calculate BMI
Run the calculation to see the BMI number and standard adult category.
- 4
Interpret with context
Consider age, muscle mass, health history, and professional medical advice.
Understanding BMI categories
Standard adult categories commonly label results below 18.5 as underweight, 18.5–24.9 as healthy weight, 25–29.9 as overweight, and 30 or higher as obesity.
A result near a boundary should not be treated as a sudden change in health. Use it as one data point and speak with a qualified clinician about personal concerns.
Private calculation in your browser
Your height and weight are processed in the browser for the calculation and do not need to be uploaded.
Try it on Kivrum
Open the real tool and follow the steps in this guide.
Frequently asked questions
Is BMI an exact measure of body fat?
No. BMI is a height-to-weight screening estimate and does not directly measure body composition.
Can I use pounds and feet?
Yes. Select imperial units and enter weight in pounds plus height in feet and inches.
Should children use adult BMI categories?
No. Children and teens require age- and sex-specific growth references interpreted by a healthcare professional.