Enter two lengths in feet and inches and choose add or subtract to calculate the combined length.

Tape measures don't give decimals — they give feet and inches, which makes ordinary addition surprisingly fiddly the moment inches carry over past 12.

How to Use the Feet and Inches Length Calculator

Fill in Length A and Length B, each as separate feet and inches fields, then choose A + B or A − B. The result updates as either length changes.

total inches = (feet × 12) + inches
result = total inches of A ± total inches of B
result feet = ⌊result inches ÷ 12⌋, remainder = result inches

Both lengths get reduced to a single inches count first, added or subtracted there, then converted back into feet-and-inches for display — the same "borrowing" a carpenter does mentally when 7" minus 9" needs to pull a foot from the other column. Decimal feet and centimeters are shown alongside for whichever unit a cut list or a metric tool actually wants.