Deck & Patio Size Calculator | LandscapeCalculating.com

Deck & Patio Size CalculatorEstimate deck boards, joists, footings, fasteners and cost for a wood or composite deck by area, span and board width.Free deck & patio size calculator with formulas, waste factors, cost estimates and professional guidance.Formula: board linear ft = area ÷ ((board width + gap) ÷ 12) × (1 + waste %); joists = (length × 12 ÷ spacing) + 1How to use this calculator

Enter deck area with length and width, then the board width and gap you are using.

Set joist spacing to 16 in for wood, 12 in for composite, and post spacing by your beam span.

Carry 10–15% cut waste and let the calculator total boards, joists, footings and fasteners.

Frequently asked questions

How do I calculate how many deck boards I need?

Divide the deck area by the board coverage (board width plus gap, in feet), then add 10–15% cut waste. This tool returns linear feet and a 16 ft board count.

How many joists do I need for a deck?

Divide the deck length in inches by the joist spacing and add one. At 16 in on center over a 16 ft span that is 13 joists.

How many footings does a deck need?

Multiply (length ÷ post spacing + 1) by (width ÷ post spacing + 1). At 8 ft post spacing on a 16 × 12 ft deck that is 12 footings.

How much does a deck cost to build?

Installed deck cost typically runs $25–$60 per sq ft for wood and $40–$85 for composite; this calculator totals materials and labor for your exact size.

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