Calculate how many deck boards, joists, beams, posts, and concrete footings you need to build a deck. Get a complete material list and cost estimate for your project.
Deck dimensions & design Full material list
ft
ft
Framing details
Material pricing (optional)
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5/4×6×16 PT: $15–$25
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2×8×16 PT: $18–$28
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4×4×8 PT: $12–$20
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16 × 12 ft deck — 192 sq ft
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Deck boards
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Joists
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Posts
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Concrete bags
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Joist hangers
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Deck sq ft
Total material cost estimate—
Deck area—
Board width + gap—
Boards across (before waste)—
Waste factor—
Total deck boards needed—
Joists (incl. rim joists)—
Posts needed—
Concrete bags (3 per post)—
Railing (linear ft perimeter)—
Total material cost—
Frequently asked questions
How many deck boards do I need? ›
Divide the deck width by the effective board width (board width + gap). For a 12 ft wide deck with 5.5 in boards and 1/4 in gaps: 144 in ÷ 5.75 in = 25.04, round up to 26 boards. Then add 10–15% for waste and end cuts. If boards run lengthwise across a 16 ft deck, you need one board per row (for 16 ft boards). This calculator handles all of that automatically.
What is the best decking material? ›
Pressure-treated pine (5/4×6 boards) is the most affordable at $2–$4/linear ft and lasts 15–20 years with staining. Cedar and redwood are naturally rot-resistant, look beautiful, and cost $3–$6/linear ft. Composite decking (Trex, TimberTech) costs $4–$8/linear ft but requires almost zero maintenance and lasts 25–30 years. For low-maintenance longevity, composite is often the best long-term value.
How far apart should deck joists be? ›
16 inches on center is the standard for 5/4 decking boards. Use 12 inch spacing for composite decking installed at a diagonal, for long spans, or for extra rigidity. 24 inch spacing is only appropriate with 2× lumber or engineered decking specifically rated for that span. Always check the decking manufacturer's recommendations for maximum joist spacing — especially for composite products.
Do I need a permit to build a deck? ›
In most jurisdictions, yes — decks above 30 inches off the ground, attached to the house, or over a certain square footage (often 200 sq ft) require a building permit. Permit fees typically run $50–$300. The permit process involves submitting plans and passing inspections at framing and completion. Building without a permit can create issues when selling your home and may require demolition if discovered.
How much does it cost to build a deck? ›
DIY material costs for a pressure-treated deck typically run $15–$25 per square foot. Composite decking materials cost $25–$45 per sq ft. Professionally installed decks run $35–$60/sq ft for PT and $55–$100/sq ft for composite. A 16×12 ft (192 sq ft) pressure-treated deck costs approximately $3,000–$5,000 in materials alone, or $6,000–$12,000 installed by a contractor.
About this deck calculator
This calculator produces a complete material list for a rectangular deck — deck boards (with proper gap and waste factored in), floor joists at your chosen spacing, support posts, concrete bags for footings, and joist hangers. It also estimates railing linear footage for elevated decks.
Don't forget these materials
Beyond the main framing, a complete deck project also requires: deck screws or hidden fasteners (~1 lb per 50 sq ft), post bases and post caps, beam lumber (doubled 2×8 or 2×10 for beam spans), flashing where the ledger attaches to the house, and stain or sealant for the finished surface (~1 gallon per 250 sq ft per coat).