Calculator
Deck Material & Cost Calculator
Enter deck size, board type, and framing spacing. We’ll estimate boards, joists, posts, and screws — plus an optional cost roll-up.
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What we calculate
Three linked steps — the same sequence you see when you hit Calculate.
Area
Length × width gives the deck surface you’ll cover with boards.
Framing
Joist spacing along the length and post spacing on each side size the structure.
Materials
Board rows, stock lengths, waste, screws, and optional prices roll into an order list.
Frequently asked questions
How do you calculate how many deck boards I need?
We divide the deck width by the effective board width (actual face width plus gap), count the rows, multiply by deck length for linear feet, then divide by the stock board length you buy. A waste factor pads for cuts and mistakes.
Which way do the boards run?
This estimator assumes decking boards run along the length of the deck and joists run across the width. That matches a common layout where joists are spaced along the length.
What joist spacing should I use?
Sixteen inches on center is common for many decks; some designs use 12" or 24" depending on board type and code. Composite boards often need tighter spacing — check the manufacturer.
How are posts estimated?
We use a simple two-beam model: posts along each long side at your chosen spacing. Real decks may need more posts for stairs, landings, or wider spans.
How many deck screws do I need?
A practical rule is about two screws at each board–joist crossing. We multiply board rows by joist count by two, then round up to full boxes.
Is this accurate enough to order materials?
It is a solid planning estimate for a rectangular deck. Rails, stairs, picture-frame borders, and local code can change counts. Confirm with a supplier or builder before a large order.