Deck board coverage
How many rows of boards a deck width actually needs. The gap between boards is coverage too — leave it out and you over-order on every deck.
| Board | Face | Gap | Covers | 8′ | 10′ | 12′ | 14′ | 16′ | 20′ |
|---|---|---|---|---|---|---|---|---|---|
| 5/4x6 | 5.5" | 0.25" | 5.75" | 17 | 21 | 26 | 30 | 34 | 42 |
| 5/4x6 | 5.5" | 0.1875" | 5.6875" | 17 | 22 | 26 | 30 | 34 | 43 |
| 5/4x6 | 5.5" | 0.125" | 5.625" | 18 | 22 | 26 | 30 | 35 | 43 |
| 2x6 | 5.5" | 0.25" | 5.75" | 17 | 21 | 26 | 30 | 34 | 42 |
| 2x6 | 5.5" | 0.1875" | 5.6875" | 17 | 22 | 26 | 30 | 34 | 43 |
| 2x6 | 5.5" | 0.125" | 5.625" | 18 | 22 | 26 | 30 | 35 | 43 |
| 1x6 | 5.5" | 0.25" | 5.75" | 17 | 21 | 26 | 30 | 34 | 42 |
| 1x6 | 5.5" | 0.1875" | 5.6875" | 17 | 22 | 26 | 30 | 34 | 43 |
| 1x6 | 5.5" | 0.125" | 5.625" | 18 | 22 | 26 | 30 | 35 | 43 |
| 1x4 | 3.5" | 0.25" | 3.75" | 26 | 32 | 39 | 45 | 52 | 64 |
| 1x4 | 3.5" | 0.1875" | 3.6875" | 27 | 33 | 40 | 46 | 53 | 66 |
| 1x4 | 3.5" | 0.125" | 3.625" | 27 | 34 | 40 | 47 | 53 | 67 |
Row counts for each deck width, computed by the same engine that powers our calculators.
Reading the table
Coverage is the board face plus one gap. A 5.5" board installed with a 1/4" gap occupies 5.75" of deck. Divide the deck width by that figure and round up, because you cannot install a partial row.
Why the gap size changes the count
Look along any board row in the table. Tightening the gap from 1/4" to 1/8" adds a row on most widths, because you fit more boards into the same space. The gap is not a rounding detail — over a 12 ft width it is the difference between 26 rows and 27, a full row of boards.
Which gap to use
Wet pressure-treated lumber shrinks as it dries, so it is often laid tight or close to it and opens up on its own. Kiln-dried and composite boards do not shrink that way and are spaced at installation, typically 1/4". Composite manufacturers publish their own required gap, and it varies with temperature at install — follow their instructions over any general rule, including this page.
Work out your own deck
The decking board calculator takes your exact dimensions, board length and layout, and returns rows, linear feet and board count with the waste your layout actually creates.