Free deck calculators with 3D visualization.Build the deck.Skip the math.
The best free online deck calculator app — deck cost, joist span, footing and 118 more, every one IRC 2021 compliant, with photoreal 3D, plan view, and permit-ready PDF. No signup, no paywall. Built for DIYers and contractors.
Most-used calculators
Featured deck calculators.
The eight most-searched deck calculators — each with photoreal 3D, IRC code references, and permit-ready PDF export.
From plan to backyard
Whatever you’re building, there’s a calculator for it.
Composite, wood, multi-level, railings, stairs — price it, size it, and visualize it in seconds.
Plan your whole deck in one tool
Skip bouncing between calculators. The Deck Project Planner turns your dimensions into a complete material list, cost, 3D preview, and a PDF — or answer 3 questions to find your material first. Free, no signup.
Plan the whole project
From a rough sketch to a permit-ready plan.
Stop juggling ten tabs. The Deck Project Planner turns your dimensions into a complete material list, a real cost, a photoreal 3D preview, and an exportable PDF — in one place, free, no signup.
- Full bill of materials — boards, joists, beams, footings, fasteners
- Real-time 3D preview you can spin to any angle
- Permit-ready PDF + shareable link
Contractor-grade accuracy
Every number is backed by the 2021 IRC.
These aren't ballpark guesses. Joist and beam spans come straight from the prescriptive IRC tables, footings use frost-depth by state, and pricing reflects 2026 regional contractor rates — with the code reference shown on every result.
- Joist & beam spans from IRC R507.5 / R507.6 tables
- Frost-depth footings + load checks per state
- 2026 state-specific material & labor pricing
Why DeckMath
Every deck calculator. Free. IRC 2021 compliant.
Material, cost, joist span, footing, beam, stair and railing calculators — contractor-grade math, homeowner-friendly UX, edge-fast everywhere.
121 calculators. Every one free.
Material estimates, joist span, footing depth, beam sizing, stair rise/run, railing posts, board feet, weight loads — all permit-ready, all in one place.
IRC 2021 Compliant
Every structural calc cross-checked against International Residential Code.
Sub-second loads
Lighthouse 95+ on real phones. Edge-cached worldwide.
Cinematic 3D animations
Real-time Three.js scenes that visualize your deck as you type. See the build before you cut a board.
Embed anywhere
One line of HTML. Works in WordPress, Webflow, Wix — any CMS, any contractor site.
Mobile-first
Built for the contractor in the field. Tap-friendly. Perfect at 375px.
Pattern library
Herringbone, picture-frame, diagonal — board counts auto-adjusted.
Imperial + metric
Mix feet/inches with metric on the same form. We handle the conversion.
How it works
How the deck calculator works in 3 steps.
Enter dimensions, pick material, get instant material list, cost, and 3D preview.
Measure
Enter dimensions in feet, inches, or metric. Imperial-metric mix is fine.
Configure
Pick material, pattern, joist spacing. We handle code lookups instantly.
Visualize
Real-time 3D preview, full BOM, and cost — exportable as PDF or shareable link.
Embed anywhere
Embed any deck calculator in one line of HTML. Free for contractor sites.
Drop the snippet into your contractor site, blog, or marketing page. Theme auto-matches. Loads asynchronously — your page stays fast.
- No iframe — clean DOM, accessible by screen readers
- Auto light/dark, auto-resize, async lazy-load
- Works in WordPress, Webflow, Wix, Squarespace, Ghost, Notion
- Free up to 1,000 calculations per domain per hour
<!-- DeckMath Deck Material Calculator — free embed -->
<a href="https://deckmath.com/calculators/deck-material-calculator"
data-deckmath-calc="deck-material-calculator"
data-theme="auto">Free Deck Material Calculator by DeckMath</a>
<script src="https://embed.deckmath.com/v1.js" async></script>People also ask
Deck calculator questions, answered.
Direct answers to the most-searched deck planning questions — IRC-referenced where it matters.
How much does a deck cost to build in 2026?
A pressure-treated deck costs $25–$45 per square foot installed in 2026, while composite decks run $40–$75 per square foot. A 12×16 (192 sqft) pressure-treated deck averages $5,800; the same in mid-grade composite averages $11,500. Use the Deck Cost Calculator for state-specific labor multipliers and 2026-Q1 pricing.
What size joists do I need for my deck?
Under IRC 2021 Table R507.6, 2×8 Southern Yellow Pine joists at 16″ on-center span up to 12'10" carrying typical 40 psf residential live load. 2×10 SYP spans 16'1". 2×12 SYP spans 19'3". The Joist Span Calculator returns the exact figure for your species, size, spacing, and tributary load.
How deep should deck footings be?
Footings must extend below the local frost line per IRC R403.1.4. Typical depths: 12″ in the south (FL, TX, GA), 24″ in mid-Atlantic, 36–42″ in the north (MN, MI, ME, ND). DeckMath's Footing Calculator looks up frost depth by state and outputs diameter, concrete volume, and bag count.
Do I need a permit to build a deck?
Most US jurisdictions require a permit when the deck is over 30″ above grade, larger than 200 sqft, or attached to the house. IRC R105 sets the federal baseline; local AHJs may set lower thresholds. Permit fees average 1.2% of project value plus a $75–$400 base. Check the Deck Permit Cost Calculator for your state.
Is composite decking worth the extra cost over pressure-treated?
Composite decking pays back in 8–12 years for most homeowners. Composite costs 2–3× the upfront price of pressure-treated, but eliminates staining/sealing labor ($400–$800 every 2–3 years) and lasts 25–30 years vs PT's 10–15 years. See the 25-year TCO comparison in the Composite vs Wood guide.
How many deck boards do I need for a 12×16 deck?
A 12×16 deck (192 sqft) using standard 5.5″-wide composite boards laid parallel to the 12' side needs 53 boards at 16' length, plus 10% waste = 58 boards total. For 6″ wide x 12' boards, the count rises to 64. The Deck Material Calculator returns exact counts by board width, length, and pattern.
Are DeckMath's calculators code-compliant?
Yes. Every structural calculator validates against International Residential Code (IRC) 2021 prescriptive tables: joist span (R507.6), beam span (R507.5), footings (R507.3), frost depth (R403.1.4), guards (R312), and stairways (R311.7). Outputs include the specific code section referenced for permit office review.
Can I embed DeckMath calculators on my contractor website?
Yes — free, no signup. Drop a single script tag into any HTML, WordPress, Webflow, or Squarespace site and the calculator renders inline with your theme auto-matched. Up to 1,000 calculations per domain per hour are free. See the Embed showcase above for the snippet.
Ready when you are
Start with the free deck cost calculator. No signup, no paywall.
121 deck calculators covering material, cost, structural, stair, railing, footing, and brand-specific estimates — built for 2026 with IRC 2021 compliance baked in.