How this calculator works
It adds up your room’s perimeter, subtracts 3 feet for each doorway opening, and adds 10% for miter cuts and waste at corners.
Worked example — a 12 ft × 12 ft room with 1 doorway:
Perimeter 48 − 3 = 45 ft × 1.10 = 50 linear feet.
Perimeter 48 − 3 = 45 ft × 1.10 = 50 linear feet.
Buy slightly long
Trim is sold in fixed lengths (8, 12, 16 ft). Buy lengths that minimize seams on your longest walls, and keep the offcuts for short runs.
Frequently asked questions
How do I measure for baseboard?
Add the length of every wall (the room perimeter), then subtract the width of each doorway.
How much extra trim should I buy?
About 10% to cover miter cuts and mistakes.