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Deck Material Calculator

Rough material list logic for any deck size, then a photorealistic render of the finished deck on the actual backyard photo. Two halves of the same conversation.

By Monty, Founder, PaperPlan · Updated June 11, 2026

Try PaperPlan free — render the finished deck on your own backyard photo in about 15 seconds.

Why this page exists

Boards, joists, posts, fasteners

A clean estimating template for the major line items you need to bid a deck.

Plug in the deck size

Pick 10×10 through 20×24 and back into board count, joist count, and railing run.

See the deck on the actual yard

A material list nobody can picture is just a spreadsheet. Render the deck so the homeowner sees what they’re buying.

Faster than spreadsheet quoting

Get a phone-first estimate and render in the time it used to take to find the tape measure.

How it works

  1. Upload a backyard photo. Use any phone photo of the build site. No measurements, no CAD file.
  2. Mark the deck area. Drag to outline where the deck goes. Add stairs or a railing line if you want them.
  3. Choose material and design. Pick composite, PVC, cedar, or pressure-treated. Compare looks on the same photo.
  4. Generate the render and share. Get a photorealistic render in seconds. Send it to the homeowner or attach it to a proposal.

Deck Material Calculator

Use this as a sanity-check estimating template, not a final cut list. Once the design is agreed, your framing software or contractor will tighten the counts.

ComponentRule of thumbWorked example
Decking boardsSquare footage ÷ board coverage (most boards: 0.92 sq ft per linear foot of 5.5" board)A 16×20 deck (320 sq ft) needs roughly 350 linear feet of decking, plus 10% waste.
Joists12” or 16” on-center spans across the short axisA 16×20 deck on 16” centers needs about 16 joists at 16 ft each.
BeamsDoubled or tripled 2x10/2x12 sized to spanMost residential decks under 20 ft use a doubled 2x10 beam, span-rated.
Posts and footingsOne footing every 6–8 ft of beamA 20 ft beam needs 3–4 posts on concrete footings below frost line.
RailingLinear feet of perimeter minus the house side and any stair openingsA 16×20 deck against the house has roughly 52 ft of railing.
FastenersHidden clips for grooved composite or screws for solid boardsComposite boards typically use 1 clip per joist intersection — roughly 4 clips per linear foot of board.

Most deck failures are framing and footings, not decking. PaperPlan won’t generate engineering specs — use a span table or your local code. The render handles the visual side; you handle the structure.

Common questions

How do I calculate decking board quantity?

Take the deck square footage and divide by the coverage of one linear foot of board. For a standard 5.5" board that’s about 0.92 sq ft per linear foot. Add 10% for waste and angle cuts.

How many joists do I need for a 16x20 deck?

On 16-inch centers, a 16×20 deck needs about 16 joists (one every 16 inches across the 20 ft span, plus end joists). On 12-inch centers, it’s closer to 21.

Does this calculator size beams and footings?

No. Beam and footing sizing depends on local span tables, soil, and frost depth. Use a span table or pull a permit — the goal of this page is rough quoting, not engineering.

How does this connect to the render?

Pick the design, render the finished deck on the homeowner’s photo, then use the rough material list to back into a number. The render makes the homeowner say yes; the math defends the price.

Keep researching

  • Deck Cost Calculator — Use our deck cost calculator to estimate the price of a new deck by size and material. Compare pressure-treated, composite, and PVC, then visualize the deck on your own backyard photo.
  • Cost to Build a Deck in 2026 — How much does it cost to build a deck in 2026? See installed-cost ranges by size and material, what affects the price, and how to render the deck before you quote.
  • Composite Deck Cost in 2026 — Composite deck cost in 2026: how Trex, TimberTech, and Fiberon compare to wood per square foot installed, and how to show the upgrade visually before quoting.
  • Deck Visualizer for Real Backyards — A deck visualizer that uses your real backyard photo. Compare composite, PVC, cedar, and pressure-treated decking on the actual yard before you commit.
  • Online Deck Designer — No Download, No CAD — A photo-first online deck designer. No app download, no CAD modeling. Upload a backyard photo, choose materials, and render the finished deck in seconds.

All deck planning guides