BMI Calculator
Free · no signup · runs entirely in your browser
Open the tool →Gibbler's BMI calculator takes two numbers and gives you one back. Choose Metric (kg/cm) or Imperial (lb/in) from the unit dropdown, type in your weight and your height, press CALCULATE, and you get your BMI to one decimal place plus the category it falls into. Nothing is stored, nothing is uploaded, there is no signup, and the arithmetic happens in your browser.
The formula is the standard one: weight in kilograms divided by height in meters squared. On imperial units the tool converts first — pounds multiplied by 0.453592, inches by 2.54 — and then runs the same division, so both modes give the same answer for the same body. Switching units changes the input labels, not the result.
The categories are the standard adult bands. Under 18.5 is underweight, 18.5 to 24.9 is normal, 25 to 29.9 is overweight, and 30 or above is obese. The tool prints your number and its band, then stops, because a band is all a BMI figure can honestly give you.
That last part is worth reading twice. BMI is a screening number built for looking at populations, not for diagnosing a person. It knows your weight and your height and nothing else — not how much of that weight is muscle, not where fat sits on your body, not your age, bone density, or medical history. A lifter and a sedentary person of identical mass get an identical score. If the number surprises you or worries you, the useful next step is a conversation with a doctor, not a second opinion from another calculator.
Use it the way it was meant to be used: a rough marker you can recalculate in ten seconds, in a browser tab, with no account and no record left behind.
How to use it
- Pick Metric (kg/cm) or Imperial (lb/in) from the UNIT dropdown.
- Enter your weight and your height in the two fields.
- Press CALCULATE to see your BMI and the category it falls in.
Worked example
Take someone weighing 82 kg at 178 cm. On Metric, that is 82 divided by 1.78 squared, or 82 / 3.1684, which the tool shows as a BMI of 25.9 in the Overweight band — just past the 25.0 line. The same person in Imperial, entered as 181 lb and 70 in, converts to 82.1 kg and 177.8 cm and reads 26.0. The tiny gap is rounding in the pounds-and-inches figures, not a different formula.
FAQ
Which formula does it use?
Weight in kilograms divided by height in meters squared. Imperial entries are converted first, multiplying pounds by 0.453592 and inches by 2.54, then run through the same division.
Is BMI a diagnosis?
No. It is a screening number based only on your weight and height, so it cannot see muscle mass, body-fat distribution, age or medical history, and muscular people often score high. Treat it as a rough marker and take any real health question to a doctor.
Are my weight and height saved?
No. The calculation runs in your browser, nothing is uploaded anywhere, and no numbers are stored. Refresh the page and the fields are empty again.
Do the bands work for children?
No, these are the adult bands. BMI for children and teenagers is read against age and sex percentile charts instead, so this calculator is not the right tool for them.
Open the BMI Calculator →