OnlineFreeToolBoxHow-to guide
How to Calculate BMI Online Free
Body Mass Index (BMI) is a quick number that relates your weight to your height, and it is used as a general guide to whether your weight is in a healthy range. This guide shows how to calculate BMI with the formula, what the ranges mean, and where the number falls short — plus a free calculator that works it out instantly. Use the free BMI calculator below to work out your BMI in seconds.
How to Calculate BMI — step by step
- Enter your weight in kilograms in the “Weight (kg)” field.
- Enter your height in centimetres in the “Height (cm)” field.
- Press “Calculate BMI”.
- Read your BMI number and its category.
Tips
- The formula is weight in kilograms divided by height in metres squared. For example, 70 kg at 1.70 m is 70 ÷ (1.70 × 1.70) = 24.2.
- The usual healthy range is 18.5 to 24.9. Below that is underweight, 25 to 29.9 is overweight, and 30 and above is obese.
- Treat one result as a guide, not a diagnosis. BMI does not measure body fat or muscle, so speak to a health professional for personal advice.
Frequently asked questions
Is BMI a medical diagnosis?
No. BMI is a general screening number only; talk to a health professional for medical advice.
What BMI counts as healthy?
The usual healthy range is 18.5 to 24.9. Below that is underweight, 25 to 29.9 is overweight, and 30 and above is obese — the calculator shows the category for your result.
Should I worry about one BMI result?
Not on its own. BMI does not measure body fat, muscle or fitness, so use it as a general guide and speak to a health professional for personal advice.