How the BMI Calculator Works
Choose your unit system
Toggle between Metric (kilograms and centimeters) and Imperial (pounds, feet, and inches). The calculator automatically adjusts all labels, input fields, and placeholder values to match your selection. The toggle is clearly visible at the top of the calculator card.
Enter your weight
Type your weight into the input field. For Metric, enter your weight in kilograms. For Imperial, enter your weight in pounds. The calculator accepts values from 1 to 500 kg (or 1 to 1,100 lbs). Use whole numbers or decimals for more precise results.
Enter your height
For Metric, enter your height in centimeters (for example, 175 cm). For Imperial, enter your height using the two separate fields for feet and inches (for example, 5 feet 9 inches). The calculator converts feet and inches to total inches internally.
View your results
Your BMI. Units are converted before calculation. Categories use the unrounded result; only the display is rounded. The shortcut multiplier 703 can differ slightly from exact conversion. BMI is one screening measure, not a diagnosis or a weight goal. It does not distinguish muscle from fat and is not suitable for pregnancy.
Copy or share your result
Click the copy button to copy your BMI result (for example, "BMI: 23.1 — Normal") to your clipboard. You can paste it into a message to your doctor, a health journal, or your personal notes.
Tips for Accurate Results
- Imperial inputs are converted using 1 lb = 0.45359237 kg and 1 in = 2.54 cm. Five feet nine inches is 69 inches, not 5.9 feet.
- Units are converted before calculation. Categories use the unrounded result; only the display is rounded. The shortcut multiplier 703 can differ slightly from exact conversion.
- BMI is one screening measure, not a diagnosis or a weight goal. It does not distinguish muscle from fat and is not suitable for pregnancy.
- Optional circumference estimate. It is not a direct body-fat measurement; incomplete or implausible measurements show no estimate.
- For ages 2–19, use a validated BMI-for-age calculator. This tool shows adult ranges only.