🪵 Decking Calculator PRO
Boards, joists, screws, footings & cost — complete deck material estimate.
Deck Layout — updates as you type
Deck plan with board runs. Board count follows the span divided by board plus gap.
1 Deck Dimensions
2 Board & Joist Configuration
3 Footings & Concrete
4 Project Details
Client Details
Results
Decking Materials
Footings & Concrete
Deck Construction Guide
Show formulas, spacing rules & pro tips ▼
Formulas
Decking Boards= (Deck Width × 12) ÷ (Board Width + Gap) × Deck Length
Joists= (Deck Length × 12) ÷ Joist Spacing + 1
Screws ≈ 4 screws per board-foot of deck area, ≈ 0.5 lbs per sqft
Footings= (Length ÷ Spacing + 1) × (Width ÷ Spacing + 1)
Concrete= Footings × Volume per footing ÷ 0.60 cuft per 80lb bag
Joist Spacing Rules
- 16" OC: Standard for most decking — required for composite boards
- 24" OC: Acceptable for 2×6 or thicker lumber — saves on joist cost
- 12" OC: High-load areas or thin decking material
Footing Size Guide
- 12" dia: Light residential decks, frost-protected areas
- 16" dia: Standard residential — most common choice
- 18" dia: Heavy loads, multi-level decks, or expansive soil
Common Mistakes
- Not checking local frost line depth — footings must extend below frost line
- Using incorrect screw type — stainless or coated screws prevent rust stains
- Skipping ledger board flashing — the #1 cause of deck failure
- Not planning for board direction — boards should run perpendicular to joists
Deck — 3D Preview
Drag to rotate — Scroll to zoom
Related Calculators
Frequently used together on the same project.
Client & Quote (prints on PDF & Excel)
Adjustments (applies to exports)
Contingency is added as a separate line on the exported cost summary. Waste % is printed as an advisory reminder.
Project notes (prints on PDF & Excel)
Result compare (A/B)
| Item | Pinned | Current | Change |
|---|---|---|---|
Saved rates auto-apply from your Price Library. Advanced details stay in your browser — nothing is uploaded except inside your own PDF/Excel exports.
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✅Method, Sources & Review
Maintained by theBuildingCalc methods desk· Last reviewedSeptember 23, 2026. This calculator implements the standards and references below; every figure can be rechecked against the formulas and worked example on this page.
Results are estimates, not engineering advice. Verify against local codes and licensed professionals for structural, electrical, and gas work. See ourTerms. Spotted an error? Report it— corrections ship with the next review.