BMI Calculator
Check your Body Mass Index with metric or imperial units, plus your healthy weight range.
How to use
- Choose metric (cm, kg) or imperial (ft/in, lb) units.
- Enter your height and weight.
- Read your BMI, weight category and the healthy weight range for your height.
Frequently asked questions
What do the BMI categories mean?
Under 18.5 is underweight, 18.5-24.9 healthy, 25-29.9 overweight, and 30+ obese - per WHO adult guidelines.
Is BMI accurate for everyone?
It's a screening tool, not a diagnosis. It doesn't distinguish muscle from fat and applies differently to athletes, children, and during pregnancy.
Is my data private?
Completely - the calculation runs in your browser and nothing you enter is stored or transmitted.
Check your BMI and what it means
Body Mass Index is a quick screen relating your weight to your height, giving a single number that sorts into underweight, healthy, overweight or obese ranges. Enter your height and weight - in metric or imperial - and get your BMI instantly along with the category it falls in. It's the most widely-used first-pass indicator of whether your weight sits in a healthy range for your height, which is why doctors, insurers and fitness apps all start here.
How BMI is calculated, and its limits
BMI is weight in kilograms divided by height in metres squared (the imperial formula multiplies by 703). The standard categories: under 18.5 is underweight, 18.5-24.9 healthy, 25-29.9 overweight, 30 and above obese. Its great strength is simplicity, but it has a real blind spot - it can't tell muscle from fat. A muscular athlete can register as 'overweight' while being very lean, and BMI thresholds also differ for some populations (several health bodies use lower cut-offs for people of South and East Asian descent).
So treat BMI as a screening tool, not a diagnosis. Waist circumference and body-fat percentage add the context BMI misses - our Body Fat Calculator estimates the latter from tape measurements.
Beyond the number
If your BMI flags a concern, the useful next questions are about trend and composition, not the single reading: is your weight moving in the direction you want, and how much is muscle versus fat? For turning that into a plan, our Daily Calorie and BMR calculators estimate how much you burn and eat, and the Macro Calculator splits it into protein, carbs and fat. All of these are general estimates for information, not medical advice - a healthcare professional can interpret them for your situation.