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🪵 DeckCalcBoards · Framing · Footings · Cost

Deck material
calculator.

Enter your deck size, pick a board, and get a complete shopping list — decking, joists, beams, posts, concrete, screws and railing — with quantities you can actually take to the lumber yard.

Your deck

Everything updates live. Length runs along the house; width is how far the deck projects out.

1 · Dimensions
Floor height above ground
2 · Decking
3 · Framing
Composite usually needs 16″ or 12″
10% is standard. Use 15% for diagonal boards or lots of cuts.
4 · Extras

Your material list

Edit any unit price — totals recalculate instantly.

192sq ft deck
—deck boards
—framing boards
—est. materials

ItemQtyUnitUnit priceTotal
Estimated material cost (before tax)$0
Fasteners, hardware & concrete included

Estimates use standard residential framing practice: beams spaced about 7 ft from the ledger, posts at max 6 ft on centre, 12″-diameter footings. Always confirm spans, footing depth (frost line) and permits with your local building code — requirements vary a lot by area. Prices are editable defaults, not live store prices.

How the numbers are worked out

No guesswork — the list is built from the same formulas carpenters use on site:

Rows of decking = deck width (in) ÷ (board width + gap)
Boards = rows × ceil(board run ÷ stock length) × (1 + waste)
Joists = ceil(length (in) ÷ spacing) + 1, plus 2 rim joists
Beam lines = 1 per ~7 ft of projection from the ledger
Posts = (ceil(length ÷ 6 ft) + 1) per beam line · Footings = posts
Screws = 2 per board × every joist it crosses
Balusters ≈ 2.7 per linear ft of railing (4″ max spacing)

Framing lumber lengths are rounded up to the next standard stock length (8 / 10 / 12 / 14 / 16 ft), because a 13-ft span still needs a 14-ft board — and the offcut rarely goes to waste on a real build.

Three ways to cut the bill

  • Size the deck to your boards. A 16-ft deck with 16-ft boards has zero decking offcuts. A 17-ft deck nearly doubles board joints.
  • Don't over-space joists. 24″ spacing saves a few joists but makes composite feel spongy — most composite warranties require 16″ max.
  • Buy the waste, skip the second trip. 10% extra lumber is far cheaper than a mid-weekend delivery run.

Deck building questions

How many boards do I need for a 12×16 deck?

With standard 5½″-wide boards and a 3/16″ gap, a 12×16 deck needs 26 rows. Using 16-ft boards that run the full length, that's 26 boards before waste — 29 with the standard 10% allowance. This calculator does that exact maths for any size.

Do I really need footings for every post?

Yes. Each post sits on its own footing sized to carry its share of the load down to undisturbed soil below the frost line. Deck collapses are overwhelmingly a footing and ledger problem, not a decking problem.

Composite vs. pressure-treated — which is cheaper?

Pressure-treated is roughly a third of the upfront board cost, but needs staining/sealing every 1–2 years. Composite costs more now and almost nothing to maintain. Over 15 years the two are surprisingly close — switch the material above and compare the totals.

What joist spacing should I use?

16″ on centre is the standard for wood and most composite. Go 12″ for diagonal boards, heavy loads (hot tubs), or a noticeably stiffer feel. 24″ is only suitable for 2×6 wood decking laid flat — never for composite.

Does this include the cost of labour or permits?

No — this is materials only. Professional installation typically adds $15–$35 per sq ft depending on region and complexity, and permits usually run $100–$500. The per-sq-ft material figure shown above is the number to compare against contractor material quotes.

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How the deck material calculator works

This deck material calculator turns your deck’s dimensions into a complete lumber-yard shopping list. Enter the length, width, height, and whether the deck attaches to the house or stands free, pick your board — pressure-treated pine, cedar, composite, PVC, or ipe — and it works out every component: decking boards, joists, beams, posts, concrete footings, screws, and railing with balusters. Framing lumber is rounded up to standard stock lengths, a 10% waste allowance is built in, and everything updates live as you change a number, so you can watch the board count move as you resize the deck. The page also covers joist spacing guidance, a composite-versus-pressure-treated cost comparison, and three practical ways to cut the bill — including sizing the deck to your board lengths to eliminate offcuts.

What goes into your shopping list

The list is built from the same formulas carpenters use on site: decking rows come from the deck width divided by board width plus gap, joists from the length divided by your spacing plus rim joists, and posts from beam lines spaced roughly every seven feet of projection. Presets for common sizes — 12×10 up to a 32×16 pool deck — give you a starting point in one tap, and the cost estimate totals the bill so you can compare materials before you buy.

Working on the roof too? The roof pitch calculator converts pitch formats and works out rafter length and true roof area the same way this page builds a materials list. Both are part of all free tools.

Frequently asked questions

How does the deck material calculator build the shopping list?

From your dimensions and board choice, it applies standard carpentry formulas: rows of decking from width divided by board width plus gap, joists from length divided by spacing, beam lines roughly every seven feet of projection, and one footing per post. Balusters are spaced to the four-inch maximum, and screws are counted at two per board per joist crossing.

Does the list include a waste allowance?

Yes — quantities include a 10% waste allowance, and framing lumber is rounded up to the next standard stock length (8, 10, 12, 14, or 16 feet), because a 13-foot span still needs a 14-foot board. Buying the waste up front is far cheaper than a mid-weekend run back to the lumber yard.

Can it estimate what my deck will cost?

Yes. Once the quantities are worked out, the calculator prices the full list for your chosen board material, so you can compare pressure-treated pine against cedar, composite, PVC, or ipe on total project cost — not just the per-board price, which is where most budgets go wrong.

Which decking materials can I choose from?

Five: pressure-treated pine 5/4×6, cedar 5/4×6, composite 1×6 (Trex-style), PVC decking 1×6, and ipe hardwood. Each changes the board count and the cost estimate, and the page’s cost-cutting tips explain when the cheaper board is the smarter buy and when it is not.

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