Deck Board Count
Free Deck Board Count calculator with clear step-by-step results.
About Deck Board Count
Board count is driven by pitch - board width plus the drainage gap - not by width alone, and ignoring the gap on a large deck can leave you a row short. Rows are multiplied by the stock lengths needed to span the deck, then rounded up with a waste allowance for cuts and culls.
Formulas
Rows required
Rows = ceil(deck width / (board width + gap))
Boards to buy
Boards = ceil(rows x ceil(deck length / stock length) x (1 + waste))
Worked example
With the default values below, Deck Board Count returns Boards to buy of 56. Change any input above and every figure here is recalculated in your browser.
Inputs used
- Deck length (along the boards)minimum 0.1 m
- 4.8 m
- Deck width (across the boards)minimum 0.1 m
- 3.6 m
- Board widthaccepts 30–400 mm
- 140 mm
- Gap between boardsaccepts 0–20 mm
- 5 mm
- Board stock lengthminimum 0.5 m
- 3.6 m
- Waste allowanceaccepts 0–40 %
- 10 %
Results
- Boards to buy
- 56 boards
- Rows across the deck
- 25 rows
- Linear metres of decking
- 132.00 m
- Deck area
- 17.28 m2
Step by step
- 1Values used
- 2Rows required
- 3Boards to buy
- 4Boards to buy= 56 boards
- 5Rows across the deck= 25 rows
- 6Linear metres of decking= 132.00 m
- 7Deck area= 17.28 m2
Assumptions and limits
- The result is derived only from the 6 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 2 decimal places, 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 wide should the gap be?
Four to six millimetres for kiln-dried timber and composite. Green or wet-treated timber shrinks, so it can be laid tighter at 2-3 mm and will open up as it dries.
Should I stagger the joins?
Yes, and stagger them over joists so no two adjacent rows butt at the same point. That is part of why a 10% waste allowance is realistic rather than generous.