BMI Calculator in Pounds and Feet

The BMI formula is mathematically defined as weight in kilograms divided by height in metres squared — there is no separately derived imperial version of the formula itself, only a conversion applied before or after the same underlying calculation. A calculator that accepts pounds, feet and inches directly is doing exactly the same kg/m² arithmetic underneath, just handling the unit conversion automatically so the person entering their height and weight never needs to convert 5 feet 9 inches into metres and 160 pounds into kilograms by hand before getting a result.

Because feet and inches split height across two separate numbers rather than one, the commonly used imperial shortcut formula — 703 × weight in pounds ÷ height in inches squared — bakes the pounds-to-kilograms and inches-to-metres conversions directly into that constant multiplier of 703, rather than requiring height to be manually converted to a single inches value and weight to kilograms as separate steps first. It produces an identical result to converting to metric first and applying the standard formula; it is simply a rearranged version of the same underlying calculation adapted for inputs that are naturally already in feet, inches and pounds.

A frequent manual-conversion mistake is treating the inches portion of a height as a decimal fraction of a foot rather than as a base-12 unit — 5 feet 9 inches is not 5.9 feet, it is 5.75 feet, since 9 inches is nine-twelfths of a foot rather than nine-tenths. Entering height as separate feet and inches fields rather than a single combined decimal number avoids this exact class of error entirely, since the conversion arithmetic happens automatically rather than depending on the person doing it correctly by hand first.