Deck boards calculator
PROBoard count, joists and screws for a rectangular deck.
Short answer: Boards = width × 12 ÷ (board width + gap). Joists = width × 12 ÷ spacing + 1. 12 ft wide, 5.5" boards + ⅛" gap = 25 boards; 16" o.c. = 10 joists. Enter your measurements above and the deck boards calculator returns the quantity, unit conversions and an estimated cost instantly, in imperial or metric — no sign-up needed.
What do you need to measure?
What is the answer?
Deck boards
26
16 ft each
Joists
10
Deck screws (2/joist)
520
How does the deck boards calculator work?
Boards = width × 12 ÷ (board width + gap). Joists = width × 12 ÷ spacing + 1.
What does a worked example look like?
12 ft wide, 5.5" boards + ⅛" gap = 25 boards; 16" o.c. = 10 joists.
What do people ask most?
›Board gap?
⅛" for wet composite/PT; up to ¼" for dry hardwood.
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Where can you learn more?
Read field notes on estimating and materials, or browse every calculator we make.