Free BMI Calculator Online

The BMI Calculator is a free online tool that calculates your Body Mass Index using your height and weight with support for both metric and imperial units.

Yes, it is completely free with no registration required. All calculations happen client-side in your browser.

Yes, the BMI Calculator accepts input in both metric (kg/cm) and imperial (lbs/inches) units for your convenience.

Absolutely. The BMI Calculator processes everything client-side in your browser. No data is uploaded to or stored on any server. Your content remains private on your device at all times.

Yes, the BMI Calculator is fully responsive and works on smartphones and tablets. You can use it on any device with a modern web browser -- no app download required.

No account or registration is needed. Simply open the BMI Calculator in your browser and start using it immediately. There are no sign-up walls or usage restrictions.

The BMI Calculator uses industry-standard formulas and algorithms to ensure accurate results. However, for critical financial or medical decisions, always consult a qualified professional.

Simply enter your input in the provided field, adjust any settings to your preference, and the tool will process it instantly. You can then copy the result to your clipboard or download it.

The BMI Calculator works in all modern browsers including Chrome, Firefox, Safari, Edge, and Opera. For the best experience, use the latest version of your preferred browser.

Body Mass Index is your weight in kilograms divided by the square of your height in metres, written as kg/m². For example, someone who weighs 70 kg and stands 1.75 m tall has a BMI of 70 / (1.75 x 1.75), which is about 22.9. If you work in imperial units, the equivalent formula multiplies pounds divided by height in inches squared by 703, giving the same result. The single number estimates how heavy you are relative to your height, which is why two people of different heights can weigh the same yet land in different categories. You do not need to do any of this by hand: enter your height and weight in either metric or imperial units above and the calculator returns your exact BMI instantly, then shows where it sits on the scale.

For most adults the widely used bands are underweight below 18.5, normal weight from 18.5 to 24.9, overweight from 25 to 29.9, and obese at 30 and above. A BMI inside the 18.5 to 24.9 range is generally described as healthy and is associated with lower risk of conditions such as type 2 diabetes, high blood pressure, and heart disease. These thresholds are screening guides, not strict cut-offs, and they apply to adults rather than children, pregnant people, or highly muscular athletes. This calculator splits the standard bands into eight finer segments, separating mild, moderate, and severe thinness at the low end and Obese Class I, II, and III at the high end. Enter your measurements above and it tells you your exact category plus the healthy weight range for your height in kilograms or pounds.

BMI only compares your total weight to your height; it cannot tell muscle from fat. Because muscle is denser and heavier than fat for the same volume, a lean, well-trained athlete can carry a lot of muscle and register a high BMI that wrongly labels them overweight or obese, while a sedentary person of the same score may actually have far more body fat. The index also ignores bone density, body-fat distribution, age, and ethnicity, so it works best as a quick population-level screen rather than an individual diagnosis. To add context this calculator offers optional inputs: enter your age and sex for an estimated body fat percentage, or your waist measurement for a waist-to-height ratio and risk rating. Use those advanced fields above to see a fuller picture than BMI alone provides.

BMI Prime is your BMI divided by 25, the upper limit of the normal-weight range. It turns your score into a simple ratio where 1.0 marks the very top of healthy weight: a value below 1.0 means you are within or under the normal range, while a value above 1.0 shows how far you are past it. For instance, a BMI of 27.5 gives a BMI Prime of 1.1, meaning you are roughly 10 percent above the healthy threshold. The appeal is that it expresses your position as an easy proportion rather than a raw number, making progress simpler to track over time. This calculator displays your BMI Prime automatically alongside your BMI and healthy weight range, so you can read both at once after entering your height and weight above.

There is no single ideal weight, which is why this calculator estimates it several ways. First it shows the healthy weight range for your height, the span of weights that keep your BMI between 18.5 and 24.9, so you can see how many kilograms or pounds separate you from it. If you add your age and sex in the advanced options, it also computes a target ideal body weight using four established formulas, the Devine, Robinson, Miller, and Hamwi equations, and shows them side by side so you can compare rather than rely on one figure. You can additionally set a target BMI to see the goal weight it implies and the distance to it. Open the advanced inputs above, enter your details, and read all of these estimates together to choose a realistic goal.