BMI Calculator
Calculate your Body Mass Index using metric or imperial units, with an instant category breakdown, a visual gauge, and your healthy weight range.
How to Calculate Your BMI
- Choose Metric (cm / kg) or Imperial (ft-in / lb) using the toggle pills.
- Enter your height and weight in the fields shown for your chosen unit system.
- Click "Calculate BMI" to see your BMI score, weight category, and the healthy weight range for your exact height.
- Check the gauge bar to see exactly where your BMI falls between Underweight and Obese.
- Switch unit systems any time — your inputs reset in the newly-shown fields.
Frequently Asked Questions
How is BMI calculated?
BMI is your weight in kilograms divided by the square of your height in meters (kg/m²). If you use Imperial units, the tool converts your feet/inches and pounds to meters and kilograms first, then applies the same formula.
What do the four BMI categories mean?
The tool labels a BMI under 18.5 as Underweight, 18.5-24.9 as Normal, 25-29.9 as Overweight, and 30+ as Obese — these are the standard World Health Organization thresholds used by most BMI calculators.
Is BMI accurate for everyone?
No. BMI doesn't distinguish between muscle and fat, so athletes and very muscular people are often classified as overweight despite low body fat, and it doesn't account for age, sex, or where fat is distributed in the body.
Should I make health decisions based on my BMI result?
BMI is a quick screening number, not a diagnosis. Talk to a healthcare provider for a full picture of your health, since factors like waist circumference, body composition, and family history matter too.
Why does the tool ask for feet and inches separately in Imperial mode?
Height in the US is usually expressed as feet and inches together, so the calculator adds both fields (converted to inches, then to meters) rather than requiring you to convert your height to a single number yourself.
How is the Healthy Weight Range calculated?
The tool takes your entered height and works the BMI formula backwards using the Normal-category boundaries of 18.5 and 24.9: multiplying each boundary by your height in meters squared gives the minimum and maximum weight that would keep you in the Normal BMI range at that exact height.
What does the gauge bar show?
It's a visual scale from a BMI of 15 to 40, shaded into the same four categories as the result (Underweight, Normal, Overweight, Obese), with a marker placed at your exact BMI so you can see at a glance how close you are to the next category boundary.