Deck Cost Calculator
Enter your deck size to estimate the decking boards and joists you need and what those materials cost.
These are estimates. Real jobs vary with surface, product and waste, so round up and check your product's label before you buy.
How much does it cost to build a backyard deck?
Deck cost depends on size, the decking material (pressure-treated wood, cedar or composite), the foundation, railings, stairs, permits and labor. Prices change by region and season, so enter your local prices above to estimate the decking and joist cost. The calculator does not include posts, footings, beams, railings, stairs or hardware, so ask for a full quote before you budget.
| Deck size | Area (sq ft) | Decking boards (12 ft) | Joists (16 in) |
|---|---|---|---|
| 10×10 ft | 100 | 20 | 9 |
| 12×12 ft | 144 | 29 | 10 |
| 16×12 ft | 192 | 39 | 13 |
| 20×16 ft | 320 | 64 | 16 |
How the deck calculator works
Deck area plus waste is divided by the area one board covers, and the result is rounded up. Joists run across the deck's width and are spaced along its length, with one more joist than the spaces between them. Standard 5/4×6 deck boards are about 5.5 inches wide.
Deck planning tips
Joists are commonly spaced 16 inches apart, but diagonal patterns and some composite boards need closer spacing, so follow the board maker's instructions. Most areas require a permit for a deck, especially one attached to a house, so check with your local building department.
Frequently asked questions
How many deck boards do I need?
Divide the deck area, plus about 10% waste, by the area one board covers. The calculator does this for you.
How far apart should deck joists be?
Sixteen inches on center is common. Check the decking manufacturer's limits.
Do I need a permit to build a deck?
Usually, yes, especially for attached or raised decks. Rules vary, so ask your local building department.