Deck Board Calculator
Find how many deck boards and how much linear footage you need from the deck size, board width and gap.
How it works
rows = ceil(deck width × 12 ÷ (board width + gap)) · linear feet = rows × deck length (+10% waste)
Boards run across the deck, so the number of rows is the deck width (in inches) divided by each board’s coverage — its actual face width plus the gap between boards. Multiplying rows by the deck length gives total linear feet, and adding 10% covers cuts, butt joints and defects. A standard “5/4×6” or 2×6 board is about 5.5 in wide, with a 1/8 in gap for drainage.
Worked example
A 16 × 12 ft deck with 5.5 in boards and a 1/8 in gap: each board covers 5.625 in, so 144 ÷ 5.625 = 26 rows. At 16 ft each that is 416 linear feet, about 458 ft with waste.
Frequently asked questions
What gap should I leave between deck boards?
About 1/8 in for drainage and airflow, which prevents rot and lets debris wash through. Wet or green-treated lumber shrinks as it dries, so gap it tighter (1/16 in) and it will open up on its own.
How do I avoid butt joints?
Buy boards at least as long as the deck span so each row is one continuous piece. Where a joint is unavoidable, land it centered on a joist and stagger joints between rows so they do not line up.
Which way should boards run?
Perpendicular to the joists, always. Running them diagonally looks great but uses more material (add 15% instead of 10%) and needs joists spaced closer to keep the boards from flexing.
Related calculators
Estimates only — add for waste and confirm against local building codes and supplier specs.