Decking Board Calculator

Estimate how many decking boards to buy from deck size, board size, gap, and board direction. Optional joist spacing and screw-pack inputs add a simple fastener estimate without changing the core board count workflow.

Decking Inputs

Optional joist, screw, and price fields
Fastener math stays optional so the calculator still gives a board answer even when only deck and board dimensions are known.
This calculator focuses on the core board-count workflow. For borders, breaker boards, hidden clips, or multi-section decks, check your layout plan before ordering.

Board width plus gap creates the board pitch

A decking row is not just the board width. The effective pitch is the board width plus the planned gap, with one fewer internal gaps than board rows. That boundary detail matters near the final row and is shown in the calculation breakdown.

board gap board gap board [====] ·· [====] ·· [====] <------ effective pitch ------>

Decking calculation

rows = deck width ÷ (board width + gap), adjusted for the final boardrows × board runs × (1 + waste) = boards to buy

Gap comparison

For the same board width, a 3 mm, 6 mm, or 8 mm gap changes how many rows fit. Use the gap required by the board manufacturer and the expected board movement, then use the calculator to see the consequence for the board count.

Where the simple count stops

Diagonal decking, borders, breaker boards, stairs, and picture framing usually create more cuts. Framing, spans, structural connections, and fastener selection are separate design decisions.

Decking resources