BMI Calculator
Find your Body Mass Index and category — a general estimate, not medical advice. It runs entirely in your browser, so the file never leaves your computer.
What the number is
Body Mass Index is weight divided by the square of height. It was devised in the 1830s as a way of describing populations, and it is used today as a quick screening number — one figure that can be calculated from two measurements anybody has.
Enter height and weight in metric or imperial and you get the number and the standard category it falls in.
What it is not
BMI knows two things about you: how tall you are and how much you weigh. It does not know how much of that weight is muscle, how you are built, your age, your sex, or where on your body the weight sits — and those are the things that actually relate to health.
The practical consequences are well documented. Muscular people are routinely classified as overweight by it. Older adults can carry a normal BMI while having lost significant muscle. It says nothing at all about blood pressure, blood sugar, fitness, or how someone feels.
It is a rough screening figure for populations that gets applied to individuals, which is a long way outside what it was designed for.
This is a general estimate, not medical advice
Nothing here is a diagnosis and nothing here is a recommendation. This tool deliberately has no target weight, no calorie figure and no goal setting, because a single number from two measurements is not a basis for any of that.
If you have a question about your health or your weight, a doctor or another qualified professional can consider the full picture — which includes a great deal that BMI cannot see. The calculation runs entirely in your browser and nothing is uploaded.
Questions
Common questions
What does this tool do?
It calculates your Body Mass Index (BMI) from your height and weight, and shows which standard category that number falls in. It works in metric (kg, cm) or imperial (pounds, feet/inches).
How do I use it?
Pick metric or imperial units, then enter your weight and height. Your BMI and its category appear instantly, with a scale showing where the number falls.
How is BMI calculated?
BMI is your weight divided by the square of your height — kilograms divided by metres squared, or the equivalent formula using pounds and inches. It's the standard formula used by health organizations as a quick screening number.
What do the categories mean?
The standard ranges are: under 18.5 is underweight, 18.5 to 24.9 is normal weight, 25 to 29.9 is overweight, and 30 or above is obese. These are general screening categories, not a diagnosis.
Is BMI an accurate measure of health?
No — BMI is only a rough screening number based on height and weight. It doesn't account for muscle, build, age, sex, or where you carry weight, so it can be misleading for athletes, older adults, and many others, and it says nothing about your overall health. Treat it as a general reference only.
Is this medical advice?
No. This tool is a general estimate, not medical advice, and it isn't a diagnosis. For anything about your health or weight, talk to a doctor or another qualified health professional who can consider the full picture. Everything is calculated in your browser; nothing is uploaded.
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