BMI Calculator
Calculate body mass index from height and weight, with adult BMI categories and a healthy-weight range.
How do I calculate my BMI?
Body mass index is your weight in kilograms divided by the square of your height in metres, and the same figure can be worked out from pounds and inches.
Formula: Body mass index divides weight in kilograms by height in metres squared: BMI = weight kg ÷ height m². Imperial entries are converted to metric first, so pounds and inches use the same formula after conversion.
What this calculator does
Enter height and weight in metric or imperial units to calculate BMI, see the adult category band, and review the assumptions and limitations of BMI as a screening measure.
Use it to turn Units, Height, Weight, Height (feet), and the other shown inputs into a checked result you can compare, copy, or rerun with different assumptions.
The page shows the formula, a numeric worked example, and the assumptions that affect this health & fitness calculation.
Inputs and what they mean
- Units
- — choice value.
- Height
- — number value.
- Weight
- — number value.
- Height (feet)
- — number value.
- Height (inches)
- — number value.
- Weight
- — number value.
How to use it
- Choose metric (cm and kg) or imperial (feet, inches and pounds).
- Enter your height. In imperial, fill in feet and inches; inches may be zero.
- Enter your weight in the matching unit.
- Read the BMI figure, adult category, and healthy-weight range estimate.
Formula
Metric method: height metres = height centimetres ÷ 100, then BMI = kg ÷ metres².
Imperial conversion method: total inches = feet × 12 + inches; metres = total inches × 0.0254; kilograms = pounds × 0.45359237.
Adult categories shown are underweight below 18.5, healthy weight from 18.5 to 24.9, overweight from 25.0 to 29.9, and obese from 30.0 upward.
The healthy weight range is calculated by rearranging the BMI formula: weight = BMI × height², using 18.5 and 24.9 as the endpoints.
Body mass index divides weight in kilograms by height in metres squared: BMI = weight kg ÷ height m². Imperial entries are converted to metric first, so pounds and inches use the same formula after conversion.
Inputs used: Units, Height, Weight, Height (feet), Height (inches), Weight.
Worked example
175 cm and 70 kg
- Convert height from centimetres to metres: 175 ÷ 100 = 1.75 m.
- Square the height: 1.75 × 1.75 = 3.0625 m².
- Divide weight by squared height: 70 ÷ 3.0625 = 22.857.
- Round to one decimal place: BMI = 22.9, which falls in the 18.5–24.9 healthy-weight category.
Reading the result
The headline figure is the main answer. Any breakdown underneath shows the parts that make it up, so you can check the working and see what changes when you adjust an input.
Limitations and assumptions
- BMI is intended as a general adult screening measure and does not account for muscle mass, bone density, body composition, pregnancy, age, or ethnicity.
- The category labels are not a medical diagnosis and can be misleading for athletes, older adults, children, and people with certain health conditions.
- Very large or very small entries can produce unrealistic BMI values; results above 200 are rejected as likely input errors.
- Estimate for informational purposes only; not medical advice, diagnosis or treatment.
- Inputs outside the supported range are rejected rather than forced into a result.
Common questions
How do I calculate my BMI?
Body mass index is your weight in kilograms divided by the square of your height in metres, and the same figure can be worked out from pounds and inches. Check the formula, example, and limitations on this page before using the result for a real health & fitness decision.
What is a healthy BMI?
For most adults, 18.5 to 24.9 is commonly treated as the healthy BMI range. Below 18.5 is underweight, 25.0 to 29.9 is overweight, and 30.0 or above is obese.
Is BMI accurate for athletes?
Not always. BMI uses only height and weight, so muscular people can have a high BMI even when their body-fat level is not high.
Does BMI diagnose health risk?
No. BMI is a screening measure, not a diagnosis. A clinician may also consider waist measurement, blood pressure, lab results, age, ethnicity, pregnancy status, medications, and medical history.
How do I use the BMI Calculator?
Enter the required values for Units, Height, Weight, Height (feet), Height (inches), and the other fields shown. The calculator applies the formula on this page and shows the main result with any supporting breakdown so you can check the arithmetic.
What formula does the BMI Calculator use?
Body mass index divides weight in kilograms by height in metres squared: BMI = weight kg ÷ height m². Imperial entries are converted to metric first, so pounds and inches use the same formula after conversion. The visible formula section above lists the calculation path and the edge cases the page handles, so the result can be checked without relying on the form alone.
Cite this page
Free Calculator. (n.d.). BMI Calculator. https://freecalculator.tech/tools/bmi-calculator
"BMI Calculator." Free Calculator, https://freecalculator.tech/tools/bmi-calculator.
BMI Calculator — Free Calculator, https://freecalculator.tech/tools/bmi-calculator
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