BMI Calculator
Find your Body Mass Index in metric or imperial — and what the number actually means.
BMI (Body Mass Index) is your weight divided by your height squared. In metric it's kilograms ÷ metres²; in imperial it's 703 × pounds ÷ inches². A 70 kg adult who is 1.75 m tall has a BMI of 22.9. Adult ranges: under 18.5 is underweight, 18.5–24.9 normal, 25–29.9 overweight, and 30 or above obese. Enter your numbers to see your BMI and category.
This calculator is for general education only and is not medical advice, diagnosis, or treatment. It is not a substitute for a qualified healthcare professional. If you have concerns about your weight or health, talk to your doctor.
Your BMI
Within the range associated with lower weight-related health risk for most adults.
Adult screening ranges (WHO/CDC). BMI doesn't distinguish muscle from fat and isn't a diagnosis — see the notes below.
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About the BMI Calculator
Body Mass Index is a quick screening number that relates your weight to your height. The math is simple: in metric, divide your weight in kilograms by your height in metres squared; in imperial, multiply your weight in pounds by 703 and divide by your height in inches squared. This calculator does both — switch units with the toggle and it recalculates instantly. The result is placed on the adult ranges defined by the World Health Organization and used by the CDC: below 18.5 is underweight, 18.5 to 24.9 is the normal range, 25 to 29.9 is overweight, and 30 or above is obese. What BMI is not is a diagnosis. It's a population-level screening tool, and it has real blind spots. It can't tell muscle from fat, so very muscular people can read as overweight while carrying little fat. It doesn't account for where fat is stored, which matters for health. And these adult cut-points do not apply to children and teenagers, who are assessed on age- and sex-specific percentiles, or to pregnancy. Treat your number as one data point that can start a conversation with a clinician — not as a verdict on your health. If your result surprises or worries you, that conversation is the right next step.
Frequently asked questions
How is BMI calculated?+
BMI is your weight divided by the square of your height. Metric: kilograms ÷ (metres)². Imperial: 703 × pounds ÷ (inches)². For example, 70 kg at 1.75 m is 70 ÷ (1.75 × 1.75) = 22.9. This tool does the conversion for you in either unit system.
What is a healthy BMI range?+
For adults, the World Health Organization defines 18.5 to 24.9 as the normal range. Below 18.5 is underweight, 25 to 29.9 is overweight, and 30 or above is obese. These are screening ranges, not targets prescribed for any individual.
Is BMI accurate for everyone?+
No. BMI is a general screening tool and has known limitations: it can't distinguish muscle from fat, so athletes and very muscular people may read high, and it doesn't reflect where fat is carried. It also doesn't apply to under-18s or pregnancy. Use it as one signal alongside professional guidance, not a standalone verdict.
Does BMI work for children and teens?+
Not with these ranges. For anyone under 18, BMI is interpreted against age- and sex-specific percentile charts rather than the fixed adult cut-points, because healthy body composition changes with growth. This calculator uses the adult ranges, so it isn't the right tool for a child's BMI.
Is this medical advice?+
No. This calculator is for general education only and is not medical advice, diagnosis, or treatment. It doesn't replace a qualified healthcare professional. If you have questions about your weight or health, talk to your doctor.
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