Enter your height and weight to calculate your BMI and see which general category it falls into.
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Body Mass Index was developed in the 19th century as a simple way to describe body size across large populations using only two easy-to-measure numbers: height and weight. Its main appeal is exactly that simplicity — no special equipment is needed, and the calculation takes seconds. For population-level research and general screening, it correlates reasonably well with body fat on average across large groups.
The trade-off for that simplicity is precision at the individual level. BMI can't tell the difference between muscle and fat, doesn't know your age, sex, or ethnicity (all of which shift how a given BMI relates to actual health risk), and says nothing about where on the body fat is carried, even though that distribution matters for health outcomes. This is why athletes with a lot of muscle mass often show a BMI in the “overweight” or even “obese” range despite low body fat, and why two people with an identical BMI can have very different body compositions and health profiles.
For these reasons, health organizations that publish BMI categories consistently describe it as a screening tool rather than a diagnostic one — a starting point for a conversation with a healthcare professional, not a conclusion on its own.
Written from what each site tells us about itself and how the directory works — see something off? Let us know.
In metric units, BMI is weight in kilograms divided by height in meters squared (kg/m²). In imperial units, it's weight in pounds divided by height in inches squared, multiplied by 703, which gives an equivalent result. This calculator handles the conversion for you regardless of which unit system you enter.
The commonly used adult ranges are: below 18.5 is classified underweight, 18.5 to 24.9 is classified normal weight, 25 to 29.9 is classified overweight, and 30 and above is classified obese (often further split into class I, II, and III at 30–34.9, 35–39.9, and 40+). These specific cutoffs come from World Health Organization guidance for adults and are the ones used by most general-purpose BMI calculators.
No, and this is well documented. BMI uses only height and weight, so it can't distinguish muscle from fat — a very muscular person can show a “high” BMI while having low body fat, and an older adult can show a “normal” BMI while having lost significant muscle mass. It also doesn't account for age, sex, ethnicity, or where fat is distributed on the body, all of which affect health risk independently of BMI. It's a quick population-level screening tool, not a diagnosis.
No. Child and teen BMI is interpreted completely differently — against age- and sex-specific growth-chart percentiles, not the fixed adult cutoffs used here. This tool is intended for adults only.
Treat it as one general data point, not a verdict. If you have concerns about your weight or overall health, a doctor or other qualified healthcare professional can consider your BMI alongside your medical history, body composition, and other factors this calculator can't see.
