BMI Calculator
Calculate your Body Mass Index (BMI) from your height and weight in metric or imperial units, see your weight category, and the healthy weight range for your height.
ToolsSoup's BMI Calculator is a free online tool that works out your Body Mass Index from your height and weight. Switch between metric (centimetres and kilograms) and imperial (feet, inches and pounds) units, and instantly see your BMI number, your weight category, and the healthy weight range for your height. Everything runs in your browser — no uploads, no sign-up, and the values you enter never leave your device.
What is BMI?
Body Mass Index (BMI) is a simple screening number that relates your weight to your height. It was designed to estimate whether an adult is at a healthy weight for their height across a whole population, and it sorts results into broad bands: underweight, normal weight, overweight, and obese. BMI does not measure body fat directly, but because it is quick to calculate and only needs two numbers, it is one of the most widely used health indicators in the world.
How to calculate your BMI
Calculating your BMI takes only a moment — the result updates the instant you finish typing:
- Choose Metric or Imperial units at the top.
- Enter your height (in centimetres, or in feet and inches).
- Enter your weight (in kilograms or pounds).
- Read your BMI, your category, and the healthy weight range for your height.
What is the BMI formula?
In metric units, BMI is your weight in kilograms divided by the square of your height in metres: BMI = kg ÷ m². In imperial units it is your weight in pounds divided by the square of your height in inches, multiplied by 703: BMI = (lb ÷ in²) × 703. This calculator converts imperial measurements to metric internally so both unit systems give the same result.
What do the BMI categories mean?
For adults, the standard World Health Organization (WHO) categories are: a BMI below 18.5 is underweight, 18.5 to 24.9 is normal (healthy) weight, 25 to 29.9 is overweight, and 30 or above is obese. These ranges are the same regardless of age or sex for adults, which is why a single BMI number can be classified at a glance.
Why use this BMI calculator?
- Calculates BMI in both metric and imperial units with one click.
- Shows your weight category — underweight, normal, overweight, or obese.
- Tells you the healthy weight range for your exact height.
- Updates instantly as you type, with no Calculate button to press.
- Runs entirely in your browser — your height and weight are never uploaded.
- 100% free with no ads, sign-up, or limits, and a one-click clear to start over.
Frequently asked questions
How is BMI calculated?
BMI is your weight in kilograms divided by your height in metres squared (kg ÷ m²). For imperial units, multiply weight in pounds divided by height in inches squared by 703. Enter your height and weight above and the tool does the maths instantly.
What is a healthy BMI?
For most adults a BMI between 18.5 and 24.9 is considered a healthy weight. Below 18.5 is underweight, 25 to 29.9 is overweight, and 30 or above is obese, following the standard WHO categories.
Is BMI accurate for everyone?
BMI is a useful screening tool but not a diagnosis. It does not distinguish muscle from fat, so very muscular people may register as overweight while the figure can underestimate body fat in others. Athletes, older adults, pregnant people, and children should treat BMI with caution and consult a healthcare professional.
Does this work in both metric and imperial units?
Yes. Use the Metric / Imperial toggle to enter your height in centimetres and weight in kilograms, or your height in feet and inches and weight in pounds. The healthy weight range is shown in the units you selected.
Are my measurements kept private?
Yes. All calculations run locally in your browser using JavaScript, so the height and weight you enter are never sent to or stored on any server.