Calculate lumber, fasteners, and total costs for your deck project in seconds.
| Item | Qty | Unit | Unit Cost | Total |
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Enter your deck's length and width in feet, select your preferred decking material and board size, then choose joist spacing and post spacing for framing. Adjust the waste factor slider to account for cuts, and optionally enter a labor rate per square foot. Click Calculate to see a full material list with quantities and estimated costs.
Building a deck is one of the most popular home improvement projects — and one of the most frequently over-budget. A 16×20 ft pressure-treated deck might cost $4,000 in materials alone, while the same footprint in composite can run $8,000–$12,000. Without an accurate estimate, homeowners routinely buy 15–25% too much lumber or make costly mid-project trips to the hardware store.
This calculator helps homeowners, contractors, and DIYers plan accurately before setting foot in a lumber yard. Whether you're quoting a client, applying for a permit, or just figuring out if the project fits your budget, knowing your material list in advance saves real money. Even a 10-board miscalculation on 2×6 cedar (at $4.50/linear foot) adds $400+ to your bill.
The cost multiplier feature is especially useful — lumber and labor prices in San Francisco or Honolulu can be 40–50% higher than rural Midwest markets for identical projects.
Decking boards: The number of boards = (Deck Width ÷ Board Face Width) × (Deck Length ÷ Board Length), with a waste factor applied. Face width accounts for a ¼" gap between boards.
Formula:
Joists: Count = (Deck Length ÷ Joist spacing in ft) + 1. Each joist length = deck width + 0.5 ft for overhangs.
Beams & Posts: Posts spaced at selected interval along both deck length and width perimeter. Beam count based on post rows.
Cost: Material unit prices × quantities × regional multiplier. Labor = deck area × labor $/sq ft.
The prices used are national averages as of 2024 and will vary by region, supplier, and market conditions. Use the regional multiplier to adjust, and always get current quotes from local lumber yards. This tool is best used for budgeting and planning, not as a final purchase order.
The calculator includes an estimate for concrete tube forms and bags based on post count, but does not calculate footing depth or soil conditions. Most decks require 3–4 bags of 60 lb concrete per post; frost-line depth in your region determines how deep footings must go — check local building codes.
True 2×6 boards are 1.5" thick (nominal 2") and are stronger, better for spans, and more resistant to warping. 5/4×6 boards are 1" thick, lighter, and often used for composite decking profiles. For pressure-treated framing, always use actual 2× dimensional lumber. For the surface deck boards, both work — 5/4×6 is the most common choice.
A typical 200–300 sq ft deck takes an experienced DIYer 2–3 weekends. Labor costs typically run $8–$20 per sq ft, so a 240 sq ft deck could save $1,900–$4,800 in labor. However, DIY requires permitting knowledge, tool access, and physical capability. Many municipalities require licensed contractors for decks over certain heights or square footages.