Deck Board Spacing
Find the number of deck boards spaced with gaps.
About Deck Board Spacing
With a fixed gap, each board plus its gap occupies a set width, so the number of boards is the deck span divided by that repeating unit, rounded up. Deck boards are sold as full-length pieces, and spacing affects both ventilation and how many boards the frame requires.
Formula
Deck Board Spacing
Boards = (deck width x 12 + gap) / (board width + gap)
- board width
- True width of one decking board
Worked example
With the default values below, Deck Board Spacing returns Boards Needed of 26. Change any input above and every figure here is recalculated in your browser.
Inputs used
- Deck width
- 12 ft
- Board width
- 5.5 in
- Gap between boards
- 0.125 in
- Waste allowanceaccepts 0–25 %
- 5 %
Results
- Deck Span
- 144 in
- Boards Needed
- 26
- Boards With Waste
- 27
Step by step
- 1Values used
- 2Deck Board Spacing
- 3Boards Needed= 26
- 4Deck Span= 144 in
- 5Boards With Waste= 27
Assumptions and limits
- The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
- In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
- Figures are rounded for display to whole numbers, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.
Frequently Asked Questions
How is Deck Board Spacing calculated?
Boards = (deck width x 12 + gap) / (board width + gap) With a fixed gap, each board plus its gap occupies a set width, so the number of boards is the deck span divided by that repeating unit, rounded up.
Why does Deck Board Spacing matter?
Deck boards are sold as full-length pieces, and spacing affects both ventilation and how many boards the frame requires.
What values do I need to enter?
This calculator takes 4 inputs: Deck width, Board width, Gap between boards, Waste allowance. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.