BMI Calculator
WEBCheck your body mass index and healthy weight category in metric or imperial.
A healthy BMI sits between 18.5–24.9. This is a general guide, not medical advice.
What is the BMI Calculator tool?
This BMI calculator checks your body mass index and shows which weight category it falls into — underweight, normal, overweight or obese — on a visual gauge, in metric or imperial units. BMI is your weight divided by the square of your height (kg/m²), the screening measure health authorities use worldwide to flag weight-related risk at a glance.
The standard adult ranges are: below 18.5 underweight, 18.5 to 24.9 normal, 25 to 29.9 overweight, and 30 or above obese. Set your height and weight with the sliders and the calculator places your value on the gauge instantly, so you can also see how close you sit to the next boundary — useful when you are tracking toward a goal weight over weeks.
Your measurements are processed entirely on your device: this body mass index calculator runs client-side in your browser, nothing is uploaded, and no account is needed — health numbers are exactly the kind of data that should never touch a server. It is free, works on your phone, and switches between kg/cm and lb/in in one tap. One honest caveat: BMI is a screening tool, not a diagnosis. It cannot tell muscle from fat, so very muscular people and older adults should read it with context — talk to a health professional about what your number means for you.
How to use the BMI Calculator
- Choose metric (kg, cm) or imperial (lb, in) units.
- Set your height with the height slider.
- Set your weight with the weight slider.
- Read your BMI value and weight category on the gauge — it updates instantly.
- Switch units any time to enter your numbers the way you know them.
Frequently asked questions
What is a normal BMI?
For adults, a BMI from 18.5 to 24.9 is classed as the normal range. Below 18.5 is underweight, 25 to 29.9 is overweight, and 30 or above is obese. These are the standard categories used by health authorities worldwide.
How is BMI calculated?
BMI = weight in kilograms divided by height in metres squared (kg/m²). In imperial units the formula is 703 × weight in pounds ÷ height in inches squared. The calculator applies the right formula for whichever unit system you pick.
Is BMI different for women and men?
The formula and the adult categories are the same for both. Body composition does differ between sexes — which is one of BMI's known limits — but the standard ranges are not split by sex.
How accurate is BMI?
BMI is a useful screening measure, not a body-fat measurement. It cannot distinguish muscle from fat, so athletes can read as overweight while carrying little fat, and it can understate risk in older adults. Treat it as a first indicator and discuss it with a health professional.
Is my health data private?
Yes. Your height and weight are processed entirely in your browser — they are never uploaded, stored or sent to any server. Once the page has loaded, the calculator even works offline.
Is this BMI calculator free?
Yes — free, with no sign-up, no account and no limits. Open the page and check your BMI in seconds.
Is this the same as the CDC or NHS calculator?
It uses the same standard formula and the same adult categories, so the number matches. Health-authority sites pair the result with clinical guidance; this tool focuses on being instant, private and easy on a phone, with a metric/imperial toggle and a visual gauge.
