BMI Calculator

How to use

1. 1Pick a unit system: Metric (kg and cm) or Imperial (lb plus feet and inches).
2. 2Enter your weight and height. The calculator updates live as you type, with input bounds for safety.
3. 3Read your BMI, category, healthy weight range, and the distance from the healthy band in the Result panel.
4. 4Use Switch to imperial or Switch to metric to convert your numbers between systems, or click a sample to seed realistic inputs.

About this tool

BMI Calculator computes your body mass index in your browser using the standard formula BMI = weight in kilograms divided by height in meters squared. Enter your weight and height in metric (kg, cm) or imperial (lb, ft + in) and the tool returns your BMI to one decimal place, your category from the World Health Organization adult classification (severely underweight, moderately underweight, mildly underweight, healthy weight, overweight, obese class I, obese class II, obese class III), the healthy weight range for your height (back-solved from the 18.5 to 24.9 healthy BMI window), and the exact difference in pounds or kilograms from the closest edge of the healthy range. It also shows BMI prime (your BMI divided by 25, where 1.00 is the upper edge of healthy) and the Rohrer ponderal index (kg per cubic meter) for tall or muscular builds where BMI is known to be misleading. A unit toggle preserves your numbers when you switch between metric and imperial, sample profiles seed realistic adult inputs, and a categories guide explains each band side by side. Useful for tracking your weight progress, sizing a healthy weight goal, comparing your current BMI to the standard ranges, or just answering a friend's "what is my BMI in kg" question without scrolling through ads. The calculator is intended for adults aged 20 and older. BMI does not separate fat from muscle, can over-classify athletes, and can under-classify older adults with low muscle mass, so this tool is a screening number, not a medical diagnosis. Talk to a qualified medical professional for a personal health assessment. All math runs entirely in your browser, so the weight and height you type stay on your device.

Free to use. Works in your browser. No signup, no login.