Body Mass Index (BMI) is weight in kilograms divided by height in meters squared (kg/m²). The World Health Organization (WHO) uses it as a population-level screening tool for underweight, normal weight, overweight, and obesity.

What are the WHO BMI categories?

Underweight: below 18.5 — Normal weight: 18.5–24.9 — Overweight: 25–29.9 — Obese Class I: 30–34.9 — Obese Class II: 35–39.9 — Obese Class III: 40 and above.

Is BMI the same for men and women?

The standard WHO BMI formula and cutoffs are the same for adult men and women. BMI does not directly measure body fat percentage, so athletes with high muscle mass may be classified as overweight despite being healthy.

BMI is a useful first-pass screening tool but has limitations: it does not account for muscle mass, bone density, age, or fat distribution. It is best used alongside other health indicators and professional medical advice.

What units does this calculator support?

Metric (kilograms and centimeters) and imperial (pounds, feet, and inches). All conversions are handled automatically — just pick your preferred unit system.

How is the healthy weight range calculated?

The healthy weight range corresponds to a BMI of 18.5–24.9 for your entered height. The lower bound uses 18.5 × height² and the upper bound uses 24.9 × height².

BMI Calculator

Name: BMI Calculator
Availability: InStock
Author: Nham Vu

Enter your height and weight in metric or imperial units to instantly see your BMI and WHO weight category.

Measurements

Unit System

Height

Weight

Enter your height and weight to see results.

Results update instantly as you type.

Summary

Enter your height and weight in metric or imperial units to instantly see your BMI and WHO weight category.

How it works

Choose metric (kg/cm) or imperial (lb/ft·in) units.
Enter your height in the height field.
Enter your weight in the weight field.
Your BMI and WHO category appear instantly.
Review the color-coded scale to see where you fall.
Check your healthy weight range for your height.

Use cases

Quickly check whether your weight is in a healthy range.
Switch between metric and imperial units without manual conversion.
Understand your WHO weight category (Underweight through Obese III).
Find your target healthy weight range to guide fitness goals.
Use as a baseline before starting a diet or exercise program.
Share a simple BMI snapshot with a healthcare provider.

Frequently Asked Questions

Last updated: 2026-06-09 · Reviewed by Nham Vu