glunty BMI Calculator (Metric + Imperial)
Metric or imperial input. Live BMI value and WHO weight category.
- Runs in your browser
- No sign-up
- No watermark
- No installs
This is a rough screening tool, not medical advice or a diagnosis. BMI does not measure body fat directly and does not account for muscle mass, bone density, body shape, age, sex, pregnancy, or ethnicity. Use it as a starting point only, and talk to a doctor or other qualified clinician before making any decision about your health.
What this tool does
Computes your body mass index (BMI) from a weight and a height and maps the result onto the four World Health Organization weight categories. You can enter measurements in metric (kilograms and centimeters) or imperial (pounds and feet plus inches); the tool converts imperial values to metric internally and always uses the standard formula, weight in kilograms divided by height in meters squared. Everything is calculated locally in your browser; nothing you type is uploaded.
How to use it
Pick a unit system, then type your weight and height. The BMI value and category update live as you type, so there is no button to press. Example: 70 kg at 175 cm gives a BMI of 22.9, which lands in the Normal weight band. The four bands are:
- Underweight: BMI below 18.5
- Normal weight: BMI 18.5 to 24.9
- Overweight: BMI 25.0 to 29.9
- Obesity: BMI 30.0 and above
Common use cases
- A quick self-check to see roughly where your BMI sits before a doctor visit.
- Converting between metric and imperial when a form or chart uses the other system.
- Tracking a rough trend over time alongside more meaningful measures like waist size.
- Teaching or learning how the BMI formula and its category cutoffs work.
- Filling in a fitness app, insurance form, or intake sheet that asks for BMI.
Common pitfalls
- BMI is not body fat. It cannot tell muscle from fat. Athletes and very muscular people often read as overweight or obese despite low body fat, while someone with little muscle can read as normal while carrying too much fat.
- It is an adult screen only. Children and teenagers are assessed with age and sex percentile charts, not these fixed cutoffs. Do not apply the adult bands to anyone under 18.
- Population, not diagnosis. The cutoffs come from population averages and do not fully account for age, sex, ethnicity, pregnancy, or body composition. A single BMI number is a starting point for a conversation with a clinician, not a verdict on your health.
Frequently asked questions
- How is BMI calculated?
- BMI is your weight in kilograms divided by the square of your height in meters (kg / m^2). If you enter imperial units, the tool first converts pounds to kilograms and feet plus inches to meters, then applies the same formula. For example, 70 kg at 175 cm gives 70 / (1.75 x 1.75), which is about 22.9.
- What are the standard BMI categories?
- The World Health Organization uses four adult categories: underweight is a BMI below 18.5, normal weight is 18.5 to 24.9, overweight is 25 to 29.9, and obesity is 30 or above. These cutoffs are the same for men and women. Some health bodies split obesity into further classes (class 1, 2, and 3), but the basic four are the most widely used.
- Is BMI accurate for athletes and muscular people?
- Not always. BMI is a ratio of weight to height and does not distinguish muscle from fat. A very muscular person can show a high BMI while carrying little body fat, and an older person who has lost muscle can show a normal BMI while carrying more fat than is healthy. Treat the number as a rough screen, not a body-fat measurement.
- Does this BMI calculator work for children?
- No. For children and teenagers, BMI is interpreted against age and sex percentile charts, not the fixed adult cutoffs. A BMI that looks normal on the adult scale can mean something different for a growing child. This tool is intended for adults; use a pediatric BMI-for-age chart or ask a pediatrician for anyone under 18.
- Why do metric and imperial give slightly different results?
- They should match very closely. Small differences come from rounding during unit conversion. One pound is 0.45359237 kg and one inch is 2.54 cm, so 154 pounds at 5 feet 9 inches works out to roughly the same BMI as 70 kg at 175 cm. Rounding each field to whole units introduces a difference of a tenth or two.
- Is my height and weight sent to a server?
- No. The entire calculation runs in your browser using plain JavaScript. Nothing you type is uploaded, logged, or stored. You can confirm this by opening your browser developer tools and watching the Network tab while you use the tool: there are zero requests.
Cite this tool
For academic, journalistic, or technical references. Pick a format:
Citations use 2026 as the publication year. Access date is left as a fillable placeholder where the citation style expects one.