BMI Calculator

BMI Calculator is a free, browser-based tool that works out your body mass index from your height and weight. BMI is a single number that estimates whether your weight is in a healthy range for your height, and it is the most widely used screening measure for weight categories in adults.

The formula is simple. In metric units, BMI = weight(kg) / height(m)^2. In imperial units, BMI = 703 * weight(lb) / height(in)^2. The calculator does the arithmetic and the unit conversion for you, so you can enter your details in whichever system you are comfortable with and read the result immediately.

Enter your height and weight and your BMI appears instantly, along with the category it falls into. Everything happens on this page - your measurements never leave your device.

You can compute BMI by hand, but it is easy to slip up: squaring the height, converting centimetres to metres, or remembering the 703 factor for imperial units. A calculator removes those errors and shows the category boundaries at a glance, so you know not just your number but what it means.

An online tool is also faster than a spreadsheet for a one-off check and works on any device without installing anything. The usual concern with health tools on the web is privacy - many services send whatever you type to a server. Dev Nexus is different: the calculation runs entirely in your browser with plain JavaScript. Your height and weight are never uploaded, logged or stored, and the tool keeps working even when you are offline. That makes it safe for a quick personal check without handing your data to anyone.

Start by choosing your units. If you think in kilograms and centimetres, pick metric; if you think in pounds and feet-and-inches, pick imperial. The calculator converts internally either way, so the result is identical.

Next, enter your height and then your weight. There is no need to press a button - the BMI number and its category update live as you type. If you make a typo, just correct it and the result follows.

The output has two parts: the BMI value itself, usually shown to one decimal place, and the weight category that value falls into. For example, a person undefined.undefined m tall weighing undefined kg has a BMI of about 22.9, which lands in the normal range. Reading both together tells you where you sit relative to standard thresholds.

BMI is a quick screening number rather than a diagnosis, and it shows up in plenty of everyday situations:

• Personal health checks: get a fast sense of whether your weight is in the typical healthy range for your height.
• Tracking progress: recompute your BMI over weeks or months to see the direction of a change, alongside the raw weight.
• Fitness and diet planning: use BMI as one input when setting realistic goals, together with waist measurements and activity levels.
• Doctor visits and forms: many intake forms and health apps ask for BMI, so it helps to know yours in advance.
• Comparing metric and imperial figures: confirm that a weight quoted in pounds matches the kilogram figure you expect.

When you need to convert between measurement systems more generally, reach for the Unit Converter; to work out ages or date spans for a health record, try the Age Calculator.

A few things help you read your result correctly and use it well:

• BMI is a screening tool, not a diagnosis. It flags whether a fuller assessment is worthwhile; it does not measure body fat directly or tell you how healthy you are on its own.
• It can mislead for some bodies. Very muscular people may read as overweight despite low body fat, while others in the normal range may carry excess fat. Waist measurements add useful context.
• Adult ranges only. The standard categories apply to adults aged undefined and over. Children and teens use age- and sex-specific percentile charts instead.
• Weigh yourself consistently. For tracking, measure at the same time of day under similar conditions so changes reflect real trends, not daily fluctuation.
• Discuss results with a professional. If your BMI falls outside the normal range, treat it as a prompt to talk to a doctor rather than a verdict.