BMI Calculator
A free, browser-based calculator. Runs entirely in your browser — no sign up, nothing stored.
Enter Values
How to use this calculator
- Enter your weight and height using whichever units you prefer.
- Press Calculate to see your BMI and weight category.
- Compare your result against the standard ranges below.
How it works
Body Mass Index (BMI) estimates body fat from your weight relative to your height. It is calculated as weight in kilograms divided by height in metres squared: BMI = kg ÷ m².
The standard adult categories are: under 18.5 (underweight), 18.5–24.9 (healthy), 25–29.9 (overweight) and 30 or more (obese). BMI is a quick screen, not a diagnosis — it doesn't separate muscle from fat or account for age, sex and build.
Worked example
80 kg at 1.8 m tall. BMI = 80 ÷ (1.8 × 1.8) = 80 ÷ 3.24 = 24.7, which sits in the healthy range.
Tips
- Measure height without shoes and weight at a consistent time of day.
- BMI ranges differ for children and some ethnic groups.
Frequently asked questions
Is BMI accurate for athletes?
Not always. Very muscular people can show a high BMI despite low body fat, so treat it as a general guide alongside other measures.
What is a healthy BMI?
For most adults 18.5–24.9 is considered healthy, but a health professional can advise what's right for you.
Related tools
Tip: Enter any known values to calculate the remaining results.
All calculations run in your browser. Your inputs are never saved or transmitted.