Feet & Inches Calculator

First length — whole feet. Enter the whole-foot portion of the first length. Put any remaining inches in the next field. Keep these input lengths nonnegative; subtraction can produce a negative result when the second length is larger.

First length — inches. Enter the inches left after removing the whole feet from the first length. The value must be less than 12 and may be a decimal or fraction. Do not type a second complete feet-and-inches expression into this split field.

Operation. Choose addition or subtraction for two lengths, or multiplication or division by a unitless number. Multiplying by a count scales a length; multiplying two lengths to obtain area is a different calculation.

Second length — whole feet. For addition or subtraction, enter the whole-foot portion of the second length. This is the length being added to or subtracted from the first one.

Second length — inches. Enter the remaining inches of the second length, below 12. Fractions such as 1/3, 1/32 and 1/64 are accepted as well as decimals. Carry complete feet into the feet field.

Scalar (unitless). For multiplication or division, enter the number by which the first length should be scaled. This number has no length unit and may be fractional. Zero is allowed for multiplication, but division by zero has no result.

The main length is rounded to the nearest sixteenth of an inch. An approximation mark means that fraction is not the exact result; the decimal equivalents retain smaller differences, including a tiny negative subtraction. A minus sign applies to the entire length. Use the calculated value when repeated rounded dimensions could accumulate an error.

Convert each length to an exact rational number of inches. Add/subtract lengths, or multiply/divide by a unitless scalar. Keep exact fractional arithmetic until display; round the final fraction to the nearest 1/16 in, with half-sixteenths away from zero.

Worked example: 2 ft 3 1/16 in + 1 ft 8 15/16 in = 4 ft 0 in exactly. Reversing a subtraction can produce a negative length.

Enter feet and inches in separate fields; do not type foot/inch symbols. Positive whole-number fraction denominators are supported. Negative subtraction results retain a minus sign for the entire length. Multiplying two lengths (area) is not supported.