BMI Calculator
Calculate your Body Mass Index (BMI) from your height and weight, in metric or imperial units.
- Category
- Healthy weight
This calculator provides estimates only. It is general information, not medical advice or a diagnosis, and doesn't account for your full personal health circumstances. Speak with a doctor or qualified health professional before making health decisions.
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How this calculator works
Body Mass Index (BMI) is a simple screening measure that relates your weight to your height: weight in kilograms divided by height in metres squared (kg/m²). It's widely used because it only needs two easy-to-measure numbers, though it doesn't distinguish muscle from fat.
Enter your weight and height in either metric (kilograms, centimetres) or imperial (pounds, inches) — switch units with the selector and the same formula is applied after converting to metric internally.
The standard World Health Organization categories are: below 18.5 is underweight, 18.5 to 24.9 is a healthy weight, 25 to 29.9 is overweight, and 30 or above is obese. Worked example: someone weighing 70kg at 170cm tall has a BMI of 70 ÷ 1.7² ≈ 24.2 — in the healthy weight range.
BMI is a population-level screening tool, not a diagnosis. It doesn't account for muscle mass, bone density, age, sex or body composition — a muscular athlete can have a "high" BMI without excess body fat. Use it as a starting point, not a verdict, and talk to a doctor about what a healthy weight range looks like for you specifically.
Frequently asked questions
- Is BMI accurate for everyone?
- No — it's a population-level screening tool. It can overestimate body fat in muscular or athletic people, and underestimate it in older adults who've lost muscle mass. It also isn't validated the same way across all ethnicities and body types.
- What's a healthy BMI range?
- The WHO defines 18.5 to 24.9 as the healthy weight range for most adults. Ranges can differ slightly for children, teenagers, and some population groups — a doctor can give you a range specific to your circumstances.
- Does BMI account for muscle mass?
- No. BMI only uses weight and height, so it can't distinguish muscle from fat. This is the main reason very muscular people are sometimes classified as "overweight" by BMI despite low body fat.