BMI Calculator
Calculate your Body Mass Index in metric or imperial units, see your weight category, and find the healthy weight range for your height — instantly, entirely inside your browser.
What is BMI?
Body Mass Index (BMI) is a simple screening measure that estimates whether a person's weight is proportional to their height. It's calculated by dividing weight by the square of height, and the result places you into one of four standard categories: underweight, healthy weight, overweight, or obesity. Doctors, insurers, and fitness professionals use it as a quick, low-cost first check — though it's a screening tool, not a diagnosis, since it can't distinguish muscle mass from fat mass.
This calculator works in both metric (kilograms and centimeters) and imperial (pounds, feet, and inches) units, so there's no need to convert anything by hand first. It also shows the healthy weight range for the height entered, so the result is easy to translate into an actual target weight rather than just a single number.
GuideHow to use it
How BMI is calculated
In metric units, BMI = weight (kg) ÷ height (m)². In imperial units, BMI = 703 × weight (lb) ÷ height (in)². For example, someone who is 1.75 m tall and weighs 70 kg has a BMI of 70 ÷ 1.75² = 22.9, which falls in the healthy range. The same formula, applied in reverse, gives the healthy weight range for a given height by solving for weight at BMI 18.5 and BMI 24.9 — the boundaries of the healthy category.
Why it helpsFeatures & benefits
Understanding the BMI categories
A BMI below 18.5 is classified as underweight, 18.5 to 24.9 as a healthy weight, 25 to 29.9 as overweight, and 30 or above as obesity. These thresholds come from World Health Organization guidelines and apply to most adults, but they're a population-level screening tool rather than an individual diagnosis — an athlete with a high muscle mass can register a high BMI without carrying excess fat, and the ranges aren't calibrated the same way for children, pregnant women, or older adults with reduced muscle mass.
Why this runs entirely in your browser
Weight and height are personal health details, so this calculator never sends them anywhere. The BMI formula and category lookup run in JavaScript locally in the tab, which means it keeps working offline once the page has loaded and nothing typed into it persists after the tab is closed.
Getting an accurate result
Accuracy depends entirely on the weight and height entered — use a recent measurement rather than an estimate if precision matters. Remember that BMI is one data point among many; body composition, waist circumference, and overall health markers all matter too, and a healthcare professional is better placed to interpret a BMI result in the context of an individual's full health picture.
Frequently asked questions
A few things people usually want to know before trusting the numbers.
In metric units, BMI = weight (kg) ÷ height (m)². In imperial units, BMI = 703 × weight (lb) ÷ height (in)².
BMI is a useful screening tool for most adults, but it doesn't account for muscle mass, bone density, age, or sex, so it can be less accurate for athletes, older adults, and growing children.
A BMI between 18.5 and 24.9 is generally considered a healthy weight for most adults, according to World Health Organization guidelines.
Yes. Use the toggle at the top of the calculator to switch between kilograms and centimeters, or pounds, feet, and inches.
No. All calculations run locally in your browser. Nothing entered here is sent to a server, stored, or shared.