BMI Calculator

What is the BMI Calculator?

This BMI calculator turns two everyday numbers — your height and your weight — into a single body mass index figure and tells you which standard weight category it falls into. BMI (body mass index) is a quick screening value used worldwide to get a rough sense of whether someone's weight is in a healthy range for their height. You enter the numbers, you read the result. Nothing is uploaded and there is no sign-up.

Everything is calculated locally in your browser, so your height and weight never leave your device. There is no account to create and no data saved — close the tab and your numbers are gone.

How to use it

1. Pick your unit system: Metric (centimetres and kilograms) or Imperial (feet/inches and pounds). The toggle switches both inputs at once — no second page to visit.
2. Type your height and weight. Your body mass index updates the instant you type — there is no submit button to press.
3. Read your BMI number and the highlighted band showing whether it sits in the Underweight, Normal, Overweight, or Obese range.

The whole point is the one-second answer on a single screen: open the page, drop in two numbers, read the result, and move on. It is fully responsive, so it works the same on a phone as on a desktop.

The formula behind it

The core metric formula is BMI = weight (kg) / height (m)²: divide your weight in kilograms by your height in metres, then divide again by your height in metres. The imperial equivalent is BMI = 703 × weight (lb) / height (in)². That 703 factor exists only so that pounds and inches give the same number as the metric formula — the two systems land on an identical result.

The World Health Organization's adult categories are:

• Underweight — BMI below 18.5
• Normal — BMI 18.5 to 24.9
• Overweight — BMI 25 to 29.9
• Obese — BMI 30 or above

Examples

• 170 cm and 65 kg gives a BMI of about 22.5, which lands in the Normal range.
• 5 ft 6 in and 180 lb gives a BMI of about 29.0, which lands in the Overweight range.
• 160 cm and 45 kg gives a BMI of about 17.6, which lands in the Underweight range.

Common use cases

• Tracking a milestone during a fitness or diet plan.
• Filling in a health form field that asks for your BMI.
• Comparing your number against the standard healthy band out of curiosity.
• Switching unit systems quickly when a doctor, app, or chart uses the one you are not used to.

Why use this BMI calculator

Plenty of sites calculate BMI, so this one earns its place by being faster, simpler, and more private. Metric and imperial live in a single toggle, so there is no separate "imperial BMI" page to hunt for. Instead of a bare number, you see where your BMI lands across the four categories on a visual band. And the calculation runs live in your browser with no submit button, no account, and nothing ever sent to a server.

It is part of a small set of everyday calculators. The Age Calculator works out an exact age from a date of birth, the Percentage Calculator handles percentages and percentage change, and the Tip Calculator splits a bill and adds a tip in seconds.

Important note

This tool is for general reference and information only and is not medical advice or a diagnosis. BMI does not measure body fat directly and can be misleading for athletes, very muscular people, older adults, pregnant people, and children. For decisions about your health, consult a qualified healthcare professional.

Frequently asked questions