How many boards for a 12 × 12 deck?
A 12x12 deck is 144 sq ft of surface. With standard 5.5-inch boards, a 1/4-inch gap, and 10% waste, that's 21 sixteen-foot boards.
| Board length | Boards needed (incl. 10% waste) |
|---|---|
| 12 ft | 28 |
| 16 ft | 21 |
| 20 ft | 17 |
Estimates are for planning. Confirm quantities against your measured site and product packaging before ordering, and follow local building codes.
Planning the rest of the 12x12 deck
Boards are the visible quarter of a deck project. Under them you'll frame joists at 16 inches on center (12 for composite on a diagonal), and the whole structure needs footings sized to your frost depth. For the full budget picture, see what a deck really costs, and if you're weighing this against a ground-level alternative, the comparison lives on our sister site: deck vs. patio costs. Stairs? The stair stringer calculator turns your deck height into riser and tread counts.
Frequently asked questions
How many deck boards do I need for a 12x12 deck?
Using standard 5.5 inch wide boards with a 1/4 inch gap and 10% waste, a 12x12 deck takes about 21 16-ft boards, 28 12-ft boards, or 17 20-ft boards. Match board length to your deck dimension to minimize butt joints.
How much does decking for a 12x12 deck cost?
Surface boards only: pressure-treated runs about $576 to $1,152 installed ($4 to $8/sq ft), composite about $1,728 to $3,600 ($12 to $25/sq ft). Framing, footings, railings, and stairs are separate.
What board length should I buy for a 12x12 deck?
Boards that span the full 12 ft dimension avoid butt joints entirely, so 16-ft boards are the clean choice here.