Deck Material Calculator
Plan how many deck boards you need from deck dimensions, board width, and gap spacing.
Deck boards needed
58 boards
26 boards across × 2 length(s) per run
- Deck area
- 192 sq ft
- Before waste
- 52
- Estimated cost
- $1044.00
- Board length
- 12 ft
Composite and hidden-fastener systems may require different gap spacing. Check the manufacturer span guide for joists.
How this calculator works
Deck board count is roughly deck width ÷ (board width + gap). Multiply by the number of board lengths required for the run.
This estimator assumes boards run across the shorter dimension. Add extra for stairs, picture-framing, and bad boards.
boards across = deck width ÷ (board width + gap)
- Common deck boards: 5.5" actual width (1x6)
- 1/8" to 1/4" gap is typical for drainage
- Buy 10% extra for cuts and culls
Frequently asked questions
How many deck boards do I need?
Divide the deck width by the installed width of each board (board width plus gap), then multiply by how many board lengths cover the deck length. Round up and add waste.
How much waste should I add for decking?
10% is a common DIY buffer. Complex patterns, diagonal decks, and picture-frame borders need more.
Do I need to calculate joists too?
Yes for a full material takeoff. This tool focuses on surface decking; use the stud/framing calculator for joist-style spacing math.
Related calculators
Keep planning your project with these tools, or browse the Deck & Fence category.