BMI Calculator — How to Calculate Your Body Mass Index and What It Means

BMI — Body Mass Index — is one of the most widely used health screening tools in the world. It's a simple number derived from your height and weight that gives a rough estimate of body fat. Doctors use it as a quick first-pass to flag potential weight-related health risks.

The Formula

BMI is calculated as your weight in kilograms divided by the square of your height in meters: BMI = weight (kg) / height (m)². In imperial units, it's BMI = (weight in lbs × 703) / (height in inches)².

For example, someone who weighs 70 kg and is 1.75 m tall has a BMI of 70 / (1.75 × 1.75) = 22.9.

What the Ranges Mean

The standard WHO categories are: under 18.5 is considered underweight, 18.5 to 24.9 is normal weight, 25.0 to 29.9 is overweight, and 30.0 or higher is classified as obese. These ranges were designed for adult men and women and don't apply to children or adolescents.

What BMI Doesn't Tell You

BMI has real limitations. It doesn't distinguish between muscle and fat — a muscular athlete can have a "overweight" BMI despite being in excellent health. It doesn't account for body composition, bone density, age, sex, or where you carry your weight. Visceral fat around the organs is far more dangerous than subcutaneous fat, and BMI can't tell the difference.

BMI is a screening tool, not a diagnosis. It's most useful as one data point among many — alongside waist circumference, blood work, blood pressure, and overall fitness.

Calculate Yours

Our BMI Calculator gives you instant results with a visual gauge. Enter your height and weight in metric or imperial, and see where you fall. No data is collected or stored — the calculation runs entirely in your browser.

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