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Deck Calculator

Estimate decking boards, screws, and materials for your deck.

Last updated: June 13, 2026

Calculator

Deck Length

feet

Deck Width

feet

Decking Board Width

Results

Deck Area192 sq ft

Decking Boards26 boards × 16ft

~410 linear feet

Screws / Fasteners~480

~2.5 per sq ft

Add 10% for Waste451 linear feet

How to Use This Calculator

1Enter deck length in feet.
2Enter deck width in feet.
3Enter joist spacing (12" or 16" on center).
4View board count, joist count, post count, and total estimate.

Formula Explanation

Deck material is estimated from area, with joist count based on spacing and posts based on beam span requirements.

Decking Boards = (Area × 12) ÷ Board Width + 10% waste Joists = (Length ÷ Spacing) + 1 Posts = Based on beam span (6-8 ft intervals)

Variables:

AreaDeck length × width in square feet

Joist Spacing12" or 16" on center (OC)

Board WidthNominal 5.5 inches for standard decking

Worked Examples

12×16 ft deck, 16" OC joists

1. Area = 192 sq ft
2. Boards = (192 × 12) ÷ 5.5 × 1.1 = 461 linear ft
3. Joists = (16 ÷ 1.33) + 1 = 13 joists

Result: ~42 boards (12 ft), 13 joists, 6 posts

Why Use This Calculator

Get a complete material list before shopping.
Includes waste factor for cuts and defects.
Accounts for joist spacing options.
Estimates post count based on standard spans.

336 × 280 Large Rectangle

300 × 250 Medium Rectangle

Tips & Best Practices

Use 16" OC joist spacing for standard decking, 12" OC for diagonal patterns or composite.
Pressure-treated lumber needs 6 months to dry before staining.
Always check local codes for railing requirements — typically required for decks 30" above grade.
Consider composite decking for lower maintenance despite higher upfront cost.

Common Mistakes to Avoid

❌ Not including waste factor in board count.

✅ Add 10-15% for waste from cuts, bowed boards, and defects. Diagonal patterns need 15-20% extra.

❌ Spacing posts too far apart.

✅ Posts should be spaced 6-8 feet apart maximum. Closer spacing is stronger. Check your local building code.

Frequently Asked Questions

How many boards do I need for a 12x16 deck?

Approximately 42 standard 12-foot decking boards (5.5" wide) with 10% waste factor. The exact number depends on board width and pattern.

Do I need a permit to build a deck?

Most jurisdictions require a permit for decks over 200 sq ft or 30 inches above grade. Check your local building department — unpermitted decks can cause issues when selling.

What joist spacing should I use?

16 inches on center (OC) is standard for most decking. Use 12" OC for diagonal patterns, composite decking, or heavy-use areas. Check manufacturer specs for composite products.

336 × 280 Large Rectangle

300 × 250 Medium Rectangle

Embed This Calculator

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Width

Height

<iframe src="https://redicalc.com/embed/construction/deck-calculator" width="100%" height="600" style="border:none;border-radius:12px;box-shadow:0 1px 3px rgba(0,0,0,0.1);" title="Deck Calculator — RediCalc.com" loading="lazy" allowtransparency="true"></iframe>

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Disclaimer: This calculator is provided for informational and educational purposes only. Results are estimates and should not be used as a substitute for professional advice. RediCalc.com makes no guarantees regarding the accuracy, completeness, or suitability of any calculations. Always consult a qualified professional before making financial, health, construction, or other important decisions.

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