Hardscape calculator
Deck board calculator: how many boards for your deck
The decking-only number: how many boards, how many linear feet, and what the layout you have chosen adds in offcuts.
Your project
The dimension the deck boards run along — usually the side parallel to the house.
Joists run this way, so this is the number that has to fit the joist span table.
Nominal 5/4x6 and 2x6 both measure 5.5". Narrow 4 inch boards measure 3.5".
Buying boards that span the full deck length removes every butt joint and most of the waste.
Wet pressure-treated goes down tight and shrinks. Dry or composite boards get a 3/16"-1/4" gap.
Crews typically order 5-10% extra to cover compaction, spillage and uneven subgrade.
Deck boards to buy
27
boards at 16 ft · 192 sq ft
- Linear feet of decking
- 421 lin ft
- Rows of boards across the deck
- 26 rows
- Coverage of one board
- 5.75 in wide
- Layout allowance
- 0%
- Face screws (2 per joist crossing)
- 758
- Hidden fasteners instead
- 674 clips
- Decking cost
- $884
Buy one extra board over the count. Every deck loses at least one to a crown, a split end or a knot that lands exactly where a cut cannot hide it.
The shareable link reopens this calculator with your exact inputs.
The deck board formula
Board coverage, not board width, is what divides into the deck. A 5.5 inch board with a quarter inch gap occupies 5.75 inches, so it covers 0.479 square feet per linear foot. Deck area divided by that number is the linear feet of decking to buy.
Then divide by the stock length. Sixteen-foot boards on a 16 foot deck give a clean, jointless surface; 12 foot boards on the same deck mean a butt joint in every row and blocking under each one.
Rows are useful to know before you start. Deck width divided by 0.479 gives the number of board rows, and the last row is almost never full width — plan whether the rip lands at the house wall or at the outer edge, because the outer one is the one everybody sees.
Gapping, shrinkage and layout waste
Wet pressure-treated lumber goes down butted tight, because it shrinks as it dries and opens its own gap. Kiln-dried, cedar and composite boards go down with a 3/16 to 1/4 inch gap, since they are already at their final width.
A diagonal layout looks superb and costs about fifteen percent more board, because every row ends in two angle cuts and the offcuts rarely pair up. A picture-frame border adds around eight percent and also needs extra blocking under the perimeter to land the mitres on solid framing.
Order the waste, do not hope for it. Coming up two boards short mid-build means a second delivery fee and, on composite, a real chance of a different colour lot.
Board coverage by width and gap
Square feet covered by one linear foot of board.
| Board | Face width | 1/8" gap | 3/16" gap | 1/4" gap |
|---|---|---|---|---|
| 2x4 / 4" board | 3.5" | 0.302 | 0.307 | 0.313 |
| 5/4x6 or 2x6 | 5.5" | 0.469 | 0.474 | 0.479 |
| 2x8 board | 7.25" | 0.615 | 0.62 | 0.625 |
Frequently asked questions
+How many deck boards do I need per square foot?
About 2.09 linear feet of 5.5 inch board per square foot of deck, with a quarter-inch gap. Multiply your deck area by 2.09 to get linear feet, then divide by your board length.
+How many boards are in a 10x10 deck?
100 square feet needs roughly 209 linear feet of 5.5 inch decking — 14 boards at 16 feet, or 18 at 12 feet, before waste.
+What gap should I leave between deck boards?
None with wet pressure-treated lumber, since it shrinks about an eighth of an inch as it dries. Use 3/16 to 1/4 inch with dry wood, cedar and composite, and follow the manufacturer's number on composite because it is a warranty condition.
+How much waste should I add for a diagonal deck?
Fifteen percent on top of the usual five. Every row on a 45 degree lay ends in two angle cuts, and the offcuts only reuse if the deck happens to be square.
+How many screws per deck board?
Two per joist crossing. A 16 foot board over joists at 16 inch centres crosses 13 joists, so 26 screws — about 1.8 screws per linear foot of decking overall.