Deck Calculator
Estimate materials and cost for a new deck. A 16 x 12 ft deck is 192 sq ft and needs 13 joists and 6 footings.
What this deck calculator estimates
It converts your dimensions into the main structural counts. Joists run across the width of the deck and are spaced 12, 16 or 24 inches apart. The joist count is length / spacing + 1. Footings are placed under two beam lines, one every 8 ft or so.
A 16 x 12 ft deck is 192 sq ft, needing 13 joists, 416 linear feet of 5.5 inch decking and 6 footings. At $30 per sq ft all-in the project costs about $5,760.00.
Deck cost per square foot
- Pressure treated wood: $20 to $35 installed
- Cedar and redwood: $30 to $45
- Composite: $40 to $65
Permits are required for most decks over 30 inches high or attached to the house. For a precise decking count use the deck board calculator.
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Frequently asked questions
How many joists do I need for a deck?
Divide the deck length in inches by the joist spacing and add one. A 16 ft deck at 16 inch spacing needs 13.
How far apart should deck joists be?
16 inches on center is standard. Use 12 inches for composite or diagonal decking.
How much does a deck cost?
Most decks cost $20 to $65 per square foot installed, so $4,000 to $12,000 for a 200 sq ft deck.
Do I need a permit to build a deck?
Usually yes for attached or raised decks. Check with your local building department.
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