Baseboard & Trim Calculator
Measure a room and get the linear feet of baseboard or trim you need, doorways subtracted, plus how many stock lengths to buy.
How it works
perimeter = 2 × (length + width) · net = perimeter − openings × opening width · buy = net × (1 + waste%) · pieces = ⌈buy ÷ stock length⌉
Baseboard runs the full perimeter of the room, so start with twice the length plus twice the width, then subtract each doorway that carries no trim. The waste allowance covers mitre cuts at corners and the offcuts left when a wall does not divide evenly into your stock length — inside and outside corners each waste a little material. Buying full pieces means rounding the total length up to whole boards.
Worked example
A 14 × 12 ft room has a 52 ft perimeter. Subtract one 3 ft doorway to get 49 ft, add 10% waste for 53.9 ft, and divide by 12 ft stock: 53.9 ÷ 12 = 4.5, rounded up to 5 boards.
Frequently asked questions
How much waste should I add for baseboard?
Ten percent suits a simple rectangular room. Add more — 15% or so — for rooms with many corners, bay windows or short walls, because each mitre and each wall shorter than your stock length leaves an unusable offcut.
Do I subtract door and cased openings?
Subtract full doorways and wide cased openings that get no baseboard. Leave standard doors in the perimeter only if the trim returns to the jamb — most installers subtract the opening width to be safe and keep the extra as spare.
Should I buy longer boards or more short ones?
Longer boards mean fewer joints on long walls, which look cleaner, but they are harder to transport and handle. Match stock length to your longest walls where possible so each wall is a single run.
Related calculators
Estimates only — add for waste and confirm against local building codes and supplier specs.