BMI Calculator
Calculate Body Mass Index from height and weight, with the category it falls into, in metric or imperial units. It is a quick screening number, not a diagnosis.
BMI Calculator
Calculate your Body Mass Index using metric or imperial units and view your approximate weight category.
What BMI measures, and what it misses
BMI is weight divided by height squared, a simple ratio used to screen populations into underweight, normal, overweight, and obese ranges. It is popular because it needs only two easy measurements and works at scale.
Its well-known limitation is that it does not distinguish muscle from fat or account for body composition, age, sex, or where fat is carried. A muscular athlete can read as 'overweight' while being very fit. So BMI is a starting indicator, not a verdict on health.
Using the number sensibly
Treat BMI as one data point among several.
- Use it to spot a trend over time rather than fixating on a single reading.
- Pair it with other measures like waist circumference for a fuller picture.
- Discuss any concern with a healthcare professional, who can interpret it in context.
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FAQs
How is BMI calculated?▼
Weight in kilograms divided by height in metres squared (kg/m2). The imperial version uses pounds and inches with a conversion factor. The tool does the math for whichever units you enter.
What are the standard BMI categories?▼
Commonly: under 18.5 underweight, 18.5-24.9 normal, 25-29.9 overweight, and 30+ obese. These are general adult ranges and vary for children and some populations.
Is BMI accurate for athletes?▼
Not very. BMI counts muscle the same as fat, so muscular people can score as overweight despite low body fat. For them, body-composition measures are more meaningful.
Does BMI work for children?▼
Not with adult categories. Children and teens use age- and sex-specific BMI percentiles, so this adult calculation should not be applied to them.
Should I rely on BMI alone for health decisions?▼
No. It is a screening tool, not a diagnosis. Use it alongside other measures and professional advice rather than as the sole basis for any decision.
Is my data stored?▼
No. The calculation runs in your browser, so your height and weight are not uploaded.
Why is BMI criticized?▼
Because it ignores body composition, fat distribution, age, sex, and ethnicity, so it can misclassify individuals even though it works reasonably for populations.
Does muscle weigh more than fat?▼
Muscle is denser than fat, so the same weight of muscle takes less space. Two people of equal BMI can look and be very different, which is part of BMI's limitation.
Can I use metric and imperial units?▼
Yes. Enter centimetres and kilograms, or feet, inches, and pounds, and the tool converts and computes correctly.
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