BMI Calculator

Body Mass Index is a quick, widely-used screening number that relates weight to height, used by doctors, fitness trackers, and insurance forms as a general starting point for discussing weight-related health. This calculator computes it instantly from your weight and height.

How BMI is calculated

The formula divides weight in kilograms by height in meters squared (weight ÷ height²). The result falls into one of four standard categories set by the World Health Organization: under 18.5 is considered underweight, 18.5 to 24.9 is normal weight, 25 to 29.9 is overweight, and 30 or above is classified as obese.

What BMI does and doesn't tell you

BMI is useful as a quick, free, population-level screening tool, which is why it's so widely used on medical intake forms and fitness apps. It doesn't account for muscle mass, bone density, age, or where fat is distributed on the body — a muscular athlete can show a "high" BMI despite having low body fat, and BMI categories were developed primarily from studies of adult populations, so they apply less precisely to children, pregnant women, or the elderly.

Frequently Asked Questions

Is a "normal" BMI the same as being healthy? Not necessarily — BMI is one data point among many (blood pressure, waist circumference, activity level, diet) that together give a fuller picture; it shouldn't be treated as a complete health diagnosis on its own.

Does this calculator work in pounds and inches? Currently it expects kilograms and centimeters — to convert, 1 pound equals about 0.4536 kg, and 1 inch equals about 2.54 cm.

Is my data saved anywhere? No — the calculation runs entirely in your browser using JavaScript; nothing is stored or transmitted.