Deck Board Calculator
Decking boards and screws for a deck from board size and gap — the row-by-row math, not just area.
Buy boards that span the deck in one piece where possible — butt joints on composite look bad and need double joists. Composite gaps: 5–6 mm side, 3 mm end, more in cold installs.
Formula
Deck Board Calculator is a free deck board calculator for civil engineers, contractors and quantity surveyors — instant, accurate and 100% client-side, with the governing formula and reference shown next to the result so the number can be defended, not just quoted.
About Deck Board Calculator
Decking boards and screws for a deck from board size and gap — the row-by-row math, not just area. The calculation implements rows = ⌈width ÷ (board + gap)⌉; boards = rows × ⌈length ÷ board length⌉ × 1.05 (Trex/TimberTech span & gapping charts; IRC R507). Buy boards that span the deck in one piece where possible — butt joints on composite look bad and need double joists. Composite gaps: 5–6 mm side, 3 mm end, more in cold installs.
How to use Deck Board Calculator
- 1Enter Deck length (board direction) in m.
- 2Enter Deck width in m.
- 3Enter Board face width in mm (5.5″ = 140 mm standard).
- 4Enter Gap between boards in mm.
- 5Read Boards (with 5% waste), Rows, Screws (≈2 per joist crossing) instantly — no submit button needed.
- 6Need US units? Flip the SI/Imperial toggle and every field converts.
Why use Deck Board Calculator?
- ✓Implements the standard formula — rows = ⌈width ÷ (board + gap)⌉; boards = rows × ⌈length ÷ board length⌉ × 1.05
- ✓Reference cited on-page: Trex/TimberTech span & gapping charts; IRC R507
- ✓One-click SI ⇄ Imperial toggle — values convert in place, physics stays in SI
- ✓Live worked example: the substitution recomputes from your numbers
- ✓Runs entirely in your browser — nothing uploaded, free forever
Frequently asked questions
What formula does the Deck Board Calculator use?+
It computes rows = ⌈width ÷ (board + gap)⌉; boards = rows × ⌈length ÷ board length⌉ × 1.05, per Trex/TimberTech span & gapping charts; IRC R507. The formula is displayed under the result along with a worked example substituted with your own inputs.
What should I keep in mind when using this calculator?+
Buy boards that span the deck in one piece where possible — butt joints on composite look bad and need double joists. Composite gaps: 5–6 mm side, 3 mm end, more in cold installs.
Does it include wastage?+
Yes — standard wastage/bulking factors are built in and stated in the formula line, so the quantity is an orderable number, not a bare geometric volume.
Is the Deck Board Calculator free to use?+
Yes — completely free, no sign-up, no limits. It runs client-side in your browser, so inputs stay private and results are instant even on slow connections.
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