BMI Calculator
Calculate your Body Mass Index and see where it sits on the WHO scale.
All calculations happen locally in your browser — nothing is uploaded, stored or tracked.
Choose metric or imperial
Toggle between kg/cm and lb/ft·in.
Enter height and weight
Use the sliders or type exact values.
Read your BMI
The result shows your BMI, category, BMI Prime and healthy weight range.
What Is BMI?
Body Mass Index (BMI) is a screening measure that relates your weight to your height. It was developed in the 19th century and is still the most widely used first-pass check of whether a person's weight is in a healthy range for their height.
BMI is calculated by dividing weight by the square of height. The World Health Organization categories are: below 18.5 underweight, 18.5–24.9 normal weight, 25–29.9 overweight, and 30 or more obese (subdivided into classes I, II and III).
Important Limitations
The Formula
In imperial units: BMI = 703 × weight (lb) ÷ height (in)². The calculator also shows your BMI Prime (BMI ÷ 25) and the healthy weight range for your height, which is the weight band corresponding to a BMI of 18.5–24.9.
Your data never leaves your device.
Every calculation on this site runs in your browser using vanilla JavaScript. Nothing is uploaded, stored or tracked.
- 100% local, client-side calculations
- No data stored on any server
- No tracking, no analytics, no ads scripts
- Works offline once loaded
Frequently Asked Questions
How is BMI calculated?
Divide your weight in kilograms by your height in metres squared. In imperial, multiply weight in pounds by 703 and divide by height in inches squared.
What is a healthy BMI?
The WHO defines 18.5 to 24.9 as the normal range. Below 18.5 is underweight, 25–29.9 overweight, and 30+ obese.
Is BMI accurate for athletes?
Not always. BMI cannot tell muscle from fat, so very muscular people can be classified as overweight despite low body fat.
Does BMI differ for men and women?
The same scale is used for both. Women naturally tend to have more body fat at the same BMI, but the WHO categories do not separate by sex.
Is BMI valid for children?
For children and teenagers, BMI is interpreted using age- and sex-specific percentile charts, not the adult categories.
What is the healthy weight range for my height?
The calculator shows it: it is the weight band that corresponds to a BMI between 18.5 and 24.9 for your height.