BMI Calculator (Body Mass Index)

Calculate your BMI from height and weight instantly, with the WHO category scale and healthy weight range.

100% free No sign-up Private · runs in your browser

How to use the free online bmi calculator

Pick metric (kg/cm) or imperial (lb/ft/in).
Enter your height and weight.
Your BMI and category appear instantly.
Check the healthy weight range for your height.

About this tool

Calculate your Body Mass Index from height and weight in metric or imperial units, with the WHO category (underweight, normal, overweight, obese) and a color-coded gauge. BMI is a screening tool, not a diagnosis — read our guide to understand its blind spots. Private by design: your measurements never leave your device.

Key features

Metric & imperial
WHO categories
Healthy weight range
Instant result

Privacy first: every calculation and generation runs 100% locally in your web browser using the Web Crypto API. Your input never touches a server — nothing is stored, logged or sold.

Read the guide

Health · 4 min read

What your BMI really means (and its blind spots)

Reading the BMI scale honestly, and knowing when the number doesn't tell the full story.

Frequently asked questions

The WHO classifies BMI 18.5–24.9 as normal/healthy, below 18.5 underweight, 25–29.9 overweight and 30+ obese. BMI is a screening tool, not a diagnosis — athletes may be 'overweight' by BMI yet lean.

BMI = weight (kg) ÷ height (m)². In imperial: 703 × weight (lb) ÷ height (in)². We accept both and convert automatically.

BMI doesn't distinguish muscle from fat and doesn't account for age, sex or frame. Use it as a rough guideline, and consult a doctor for health advice.