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Deck Calculator —
Exact Boards, Cost & Linear Feet

Know exactly how many boards to buy before you go to the lumber yard. Get board count, linear feet, and full project cost in seconds — free, no sign-up needed.

✅ 6 Deck Materials ✅ Board Count ✅ Gap Spacing ✅ Labor & Material Cost ✅ Any Deck Shape
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Frequently Asked Questions

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Formula: Total Deck Area (with waste) ÷ Individual Board Area = Number of Boards. Individual board area = Board Length (ft) × (Actual Board Width + Gap) in ft. Example: a 200 sq ft deck with 15% waste = 230 sq ft ÷ (12 ft × 0.479 ft for a 5.5-inch board with 0.25-inch gap = 5.75 sq ft per board) = 40 boards. Use actual board width, not nominal. Our deck calculator does this calculation automatically — enter board length, actual width, gap size, and deck area to get exact board count.
A nominal 2×6 board measures 1.5 inches thick by 5.5 inches wide after milling — not 2×6. A 5/4×6 decking board (the most popular decking size) is actually 1 inch thick by 5.25 inches wide. A 2×4 board is actually 1.5 × 3.5 inches. Always use actual dimensions when calculating deck boards — using nominal sizes will cause you to under-order by 8–10%. Our deck calculator dropdown shows both nominal and actual sizes to prevent this common mistake.
Pressure treated wood decks cost $15–$25 per sq ft installed including materials and labor, meaning a 200 sq ft deck costs $3,000–$5,000. Cedar decks run $20–$35 per sq ft ($4,000–$7,000 for 200 sq ft). Composite decks like Trex cost $30–$60 per sq ft installed ($6,000–$12,000 for 200 sq ft). Ipé hardwood decks cost $45–$75+ per sq ft. Enter your deck area and per-sq-ft material and labor costs in our free deck calculator to get a detailed cost breakdown for your specific project.
Leave 1/4 inch (6 mm) between pressure treated or cedar boards to allow for drainage and natural wood expansion in humid weather. For composite decking, follow the manufacturer's recommendation — typically 1/8 inch for hidden fasteners and 3/16 inch for face screws, as composite expands and contracts differently than wood. Never install wood boards with zero gap — they will cup and buckle after rain. Our deck calculator includes gap spacing in the board count formula so your estimate accounts for the space lost to gaps.
Pressure treated lumber lasts 15–25 years with regular maintenance every 2–3 years (cleaning and staining or sealing). Cedar naturally resists rot and insects and lasts 15–20 years with annual or biennial sealing. Untreated pine or non-pressure-treated wood lasts only 5–10 years. Composite decking such as Trex lasts 25–30 years with minimal maintenance (annual washing). IPé hardwood is the most durable, lasting 40–75 years. PVC decking lasts 30+ years and is completely immune to moisture, rot, and insects.
Choose pressure treated wood or cedar if upfront cost is the priority and you do not mind maintenance every 1–3 years. Total cost of ownership over 25 years is often similar to composite when you factor in staining, sealing, and board replacement. Choose composite (Trex, TimberTech, Fiberon) if you want a low-maintenance, splinter-free deck with consistent appearance. Composite costs 2–3 times more upfront but requires only occasional washing. For the highest durability and a premium look, IPé hardwood is the top choice despite its high cost.
Divide your total deck area (including waste) by the actual board width in feet. Example: a 230 sq ft order (200 sq ft + 15% waste) using 5.5-inch wide boards = 230 ÷ 0.458 = 502 linear feet. This tells you how many feet of board to order. Then divide by your chosen board length to get board count. Our deck calculator shows linear feet automatically in the results section alongside board count, saving you this calculation entirely.
For 5/4 decking (1 inch thick) into 2-inch joists, use 2.5-inch (10d) screws. For 2× decking (1.5 inches thick), use 3-inch (16d) screws. Always use stainless steel, hot-dipped galvanized, or coated deck screws — regular zinc screws corrode quickly outdoors, especially with pressure treated lumber which contains copper. Use 2 screws per board per joist for 2× material, and 1–2 screws per board per joist for 5/4 decking. Pre-drill near board ends to prevent splitting.

How to Calculate Deck Boards and Material Needed

Building a deck is one of the best investments you can make in your home — it adds outdoor living space and increases resale value. But accurately calculating how many boards you need, and what it will cost, is essential before you visit the lumber yard or order composite panels. Our free deck calculator handles all the math, including board gaps and waste from cuts.

The formula for deck boards is: Boards = Total Area ÷ (Board Length × (Board Width + Gap)). For example, a 200 sq ft deck using 12 ft boards that are 5.5 inches wide with a 0.25 inch gap: effective board width = 5.75 inches = 0.479 ft. Board area = 12 × 0.479 = 5.75 sq ft. With 15% waste: 200 × 1.15 ÷ 5.75 = 40 boards. Our calculator does this instantly.

Deck Material Comparison — Wood vs Composite

Material Cost / Sq Ft Lifespan Maintenance
Pressure Treated Wood $2–$5 15–25 yrs Stain every 2–3 yrs
Cedar $5–$8 15–20 yrs Seal every 1–2 yrs
Composite (Trex) $8–$15 25–30 yrs Minimal — wash only
Ipé Hardwood $15–$25 40–75 yrs Oil yearly
PVC $10–$18 30+ yrs Virtually none

Board Sizing — Nominal vs Actual Dimensions

One of the most common mistakes when calculating deck boards is using the nominal (labeled) size instead of the actual size. A 2×6 board is labeled as 6 inches wide but the actual width after milling is 5.5 inches. A 5/4×6 deck board is actually 5.25 inches wide. Always use actual dimensions in our deck board calculator — our dropdown options show both nominal and actual sizes so you never make this mistake.

Pro Tips for Deck Building

  • ▸Use hidden fasteners for composite — they give a clean surface look and are required by most composite manufacturers to maintain warranty.
  • ▸Let pressure treated wood dry — new PT lumber contains moisture. Wait 6 months before staining or sealing, otherwise the finish will peel.
  • ▸Add 15–20% for diagonal patterns — diagonal or herringbone deck layouts create more cut-off waste. Increase your waste percentage accordingly in the calculator.
  • ▸Pre-drill Ipé and hardwood — exotic hardwoods are extremely dense and will split without pre-drilled pilot holes at every fastener point.
  • ▸Use stainless or hot-dipped galvanized fasteners — regular zinc screws corrode quickly outdoors, especially near coastal areas or with pressure treated lumber.

Use our free deck calculator above for any deck shape and material type. Enter your board dimensions and gap spacing to get exact board count, linear feet, and a full material plus labor cost estimate — no sign-up required.

Before building your deck, calculate the gravel base material needed for drainage, and use our cubic yard calculator for concrete footings.

Related Calculators

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Flooring Calculator

Match your deck with interior flooring for a seamless indoor-outdoor look.

Mulch Calculator

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Deck Guides & Articles

Composite vs Wood Deck CostMost Popular

Full cost comparison — upfront vs lifetime cost, maintenance, and ROI.

How Many Deck Boards Do I Need?

Board count formula with actual vs nominal width and spacing guide.

Gravel Base for Outdoor Projects

Gravel depth and compaction guide for decks, patios, and driveways.

Square Feet to Cubic Yards

Convert deck area to cubic yards for concrete footing calculations.