SuperCalc

BMI Calculator

Check your Body Mass Index instantly. Supports metric and imperial, with healthy weight ranges and visual breakdown.

BMI Calculator

Enter your height and weight to calculate your Body Mass Index.

cm
kg

BMI Categories

WHO classification of Body Mass Index ranges.

CategoryBMI Range
Underweight
< 18.5
Normal
18.5 – 24.9
Overweight
25 – 29.9
Obese I
30 – 34.9
Obese II
35 – 39.9
Obese III
40+

How BMI works

Body Mass Index (BMI) is a simple ratio of your weight to your height squared. Devised by Belgian mathematician Adolphe Quetelet in the 1830s, it was designed as a population-level statistical tool — not an individual diagnostic. Despite its age, BMI remains the most widely used screening metric for weight-related health risk by the WHO, CDC, and NHS.

The formula is: BMI = weight (kg) / height (m)2. In imperial units, multiply by 703: BMI = (lbs / in2) × 703.

BMI Prime is the ratio of your BMI to 25 (the upper boundary of normal weight). A BMI Prime below 1.0 means you are within the healthy range. It is a quick, intuitive metric — a value of 0.90 tells you that you are 10% below the overweight threshold.

FAQ

How is BMI calculated?
BMI = weight (kg) / height (m)^2. In imperial units: (weight in lbs / height in inches^2) x 703. The formula produces a single number that maps to health risk categories established by the WHO.
What are the limitations of BMI?
BMI does not distinguish between muscle and fat, does not account for fat distribution (visceral vs. subcutaneous), and uses population-level cutoffs that may not apply to all ethnicities, ages, or body types. Athletes, elderly adults, and people of Asian descent may need adjusted interpretation.
Does age or gender affect BMI interpretation?
The formula is the same for all adults, but interpretation varies. Women naturally carry more body fat than men at the same BMI. Older adults lose muscle mass with age, so the same BMI at 70 represents more body fat than at 30. Children and teens should use BMI-for-age percentile charts instead of fixed adult categories.
What is the healthy BMI range?
18.5 to 24.9 is considered healthy (normal) weight by the WHO. This range is associated with the lowest risk of weight-related chronic diseases. Within this range, research suggests BMI 20–25 carries the lowest all-cause mortality risk.
What is BMI Prime?
BMI Prime is the ratio of your BMI to 25 (the upper limit of normal). A value below 1.0 means you are within the healthy range; above 1.0 means you have crossed into overweight territory. It gives a quick sense of how far above or below the threshold you are.
Are my numbers stored anywhere?
Only in your browser's local storage, so they survive a page refresh on this device. Nothing is sent to any server — the entire calculation runs in your browser.

Medical disclaimer: BMI is a screening tool, not a medical diagnosis. It does not measure body fat directly and does not account for muscle mass, bone density, age, sex, or ethnicity. Consult a healthcare provider for personalized health advice.

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