How to use BMI Calculator — Free Body Mass Index Calculator (Metric & Imperial)
- 1Choose metric or imperial units.
- 2Enter your weight and height.
- 3See your BMI, its category, and a healthy weight range.
About BMI Calculator
BMI is the quickest general screening number for weight relative to height, and this calculator handles both metric and imperial units so you don't need to convert anything yourself.
Alongside the number, you get the standard category it falls into, a visual gauge showing where you sit on the scale, and the weight range that would put you in the 'normal' band at your height.
As with any general screening tool, BMI doesn't capture the full picture of someone's health — it's a starting point, not a diagnosis. Everything here is calculated locally in your browser.
Frequently asked questions
How is BMI calculated?
BMI = weight in kilograms ÷ (height in metres)². The calculator does the unit conversion for you if you use imperial units.
What do the BMI categories mean?
Under 18.5 is underweight, 18.5–24.9 is normal, 25–29.9 is overweight, and 30 or above is considered obese, per the standard adult BMI ranges.
Is BMI a perfect measure of health?
No — it doesn't account for muscle mass, bone density, age, sex or where fat is distributed, so it's a general screening tool rather than a diagnosis. Talk to a doctor for personal health advice.
What is the 'healthy weight range'?
The weight range that would give a BMI between 18.5 and 24.9 at your entered height.
Is it free?
Yes, unlimited and free, with no sign-up.