Deck Calculator

Estimate the deck boards, joists, and screws you need, plus the 2026 installed cost by material from the deck's square footage. Assumes standard 5/4x6 boards (5.5 in actual width).

📅 Updated: 2026-08-15 ✍️ Author: RenoFig Research Team 📊 Data: 2026 costs (HomeAdvisor/Angi, HomeGuide) ✅ Free & No Sign-Up

Calculator Inputs

Add 1 row for typical cuts; more for diagonal layouts.

Results

Deck Area—
Deck Boards / Joists—
Installed Cost (low)—
Installed Cost (mid)—
Installed Cost (high)—

* Estimate only. Railings, stairs, footings, and permits are usually extra. Prices are 2026 national installed ranges, not a quote.

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Formula & How It Works
StepFormula
Deck areaLength × Width
Boards per row⌈ Length ÷ Board length ⌉
Rows across⌈ (Width × 12) ÷ 5.5 ⌉ + waste rows
Joists⌈ Length ÷ (Spacing ÷ 12) ⌉ + 1
Cost (low)Area × Material low $/sq ft
Cost (high)Area × Material high $/sq ft

2026 installed cost ranges per square foot (HomeAdvisor/Angi and HomeGuide, retrieved 2026-08-15): pressure-treated wood ~$25–$35, cedar ~$30–$45, composite ~$35–$60. Mid = average of low and high. Standard build assumptions: 5/4x6 deck board = 5.5 in actual width; 16 in on-center joist spacing.

Frequently Asked Questions

Installed 2026 cost ranges per square foot: pressure-treated wood ~$25–$35/sq ft, cedar ~$30–$45/sq ft, composite ~$35–$60/sq ft. These reflect national contractor cost guides (HomeAdvisor/Angi, HomeGuide) retrieved 2026-08-15. Railings, stairs, and permits are usually extra.
16 inches on center is the standard spacing for deck joists under wood and composite decking (it meets most code and manufacturer span tables). Use 12 inches for diagonal layouts or heavier loads, and 24 inches only where the decking is rated for it.
A standard 5/4x6 deck board is 5.5 inches wide actual. Divide the deck width in inches by 5.5 and round up to get boards per row, then multiply by the number of rows (deck length ÷ board length, rounded up). Always add 1 row for waste/cuts.

Related Tools

Data sources & retrieved: 2026-08-15 — 2026 installed deck cost ranges per square foot from national contractor cost guides (HomeAdvisor/Angi "Deck Installation Cost", HomeGuide "Cost to Build a Deck"): pressure-treated wood ~$25–$35, cedar ~$30–$45, composite ~$35–$60. Build assumptions: 5/4x6 deck board actual width 5.5 in; 16 in on-center joist spacing per IRC / composite-decking span tables.

Disclaimer: This tool is for educational estimation only. Railings, stairs, footings, and permits are usually extra. It does not constitute a quote or professional advice.