Use the BMI Calculator to find your Body Mass Index in seconds — a quick way to check whether your weight sits in a healthy range for your height.
Educational use only. This calculator is a general-purpose tool and does not replace medical advice. If a result surprises you or you have an underlying condition, consult a clinician before acting on it.
This tool runs entirely in your browser — no data is sent to our servers. If JavaScript is disabled, the fully interactive version will not run; enable JavaScript to compute results.
Body Mass Index (BMI) is one of the most common screening tools in primary care. It is calculated by dividing your weight in kilograms by the square of your height in metres (kg/m²). The value places you in a category — underweight, healthy, overweight or obese — and gives your clinician a fast starting point before they look at the full picture.
BMI is intentionally simple. That makes it useful at scale, but it also has real limits. Two people of the same height and weight can have very different body compositions: an athlete with above-average muscle mass will often score "overweight" on BMI even though their body fat percentage is low. The reverse is also true — someone with low muscle and high fat can sit in the "healthy" range while carrying more risk than the number suggests. Use BMI as one signal, not the whole story.
For adults, the World Health Organization defines a healthy BMI as 18.5 to 24.9. For children, teenagers, pregnant women and adults over 65, the interpretation shifts and the category boundaries differ. If your result surprises you, talk to a clinician before changing your diet or activity dramatically.
For most adults, 18.5 to 24.9 is the healthy range. Below 18.5 is underweight, 25 to 29.9 is overweight, and 30 or above is in the obese range. These thresholds were set by the WHO based on population-level risk and may shift slightly for athletes, children and older adults.
Often not. Muscle is denser than fat, so muscular athletes commonly score "overweight" or even "obese" on BMI even when their body fat is low. For anyone with substantial muscle mass, a body fat percentage measurement is a more meaningful number.
No. Children and teenagers are measured against age-and-sex-specific growth charts (BMI-for-age percentiles), not the adult thresholds. Use your paediatrician's chart for anyone under 18.
No. The calculation runs entirely in your browser. Your numbers never leave your device and are not saved or shared.
For most adults, once a month is plenty. For people actively trying to lose or gain weight, weekly is fine — daily readings tend to add noise rather than signal.
The BMI Calculator lives alongside Body Fat Percentage Calculator, Ideal Weight Calculator, Smart Calorie Calculator (BMR & TDEE) on the Health & Fitness page. That landing page collects every health & fitness tool Dailiyo publishes, plus the editorial notes on formula sources, review cadence and how each result should (and should not) be interpreted. If a related health & fitness calculation isn't yet in the collection and you'd like to see it, drop a line via the contact page — the editorial team reviews every request and prioritises tools that come up most often in reader questions.