Deck Calculator
Estimate deck boards, framing, and total project cost
Length of deck
Width of deck
Nominal width
16" standard, 12" composite
Deck Area
—
sq ft
Deck Boards
—
boards
Joists Needed
—
joists
Footings Needed
—
footings
Estimated Cost
—
USD
Disclaimer: Results are estimates based on standard formulas. Not a substitute for professional advice from a licensed contractor, engineer, or architect. Verify all calculations before making purchasing or construction decisions.
How to Use This Calculator
A well-planned deck starts with accurate material estimates. Our calculator helps you determine boards, joists, and footings.
- Measure deck length and width
- Choose decking material
- Select joist spacing
- Enter specifications
- Add 10-15% waste
Expert Insights
Smart analysis for your Decking project
Wood vs Composite TCO
Pressure-treated: $15-25/sqft, lasts 15 years. Composite: $30-60/sqft, lasts 25-50 years with zero annual sealing. AI compares true lifetime cost.
Joist Spacing Intelligence
16" OC for wood decking, 12" OC required for most composite. AI checks your material choice and adjusts joist count automatically.
Ledger Board Safety
#1 deck failure source: improper house attachment. AI flags critical flashing and lag bolt requirements for code-compliant installation.
Calculation Formula
Area = L x W
Boards per row = ceil(W x 12 / Board width)
Boards per section = ceil(L / 16) (standard 16 ft board length)
Boards = ceil(Boards per row x Boards per section x 1.10) [+10% waste]
Joists = (L x 12 / Joist spacing) + 1
Decking Material Comparison
| Material | Cost/Sq Ft | Lifespan | Annual Maintenance | Joist Spacing |
|---|---|---|---|---|
| Pressure-Treated Pine | $15-25 | 15-20 years | Seal yearly | 16" OC |
| Cedar/Redwood | $25-40 | 20-30 years | Seal every 2-3 yrs | 16" OC |
| Composite (Basic) | $30-45 | 25-30 years | Wash only | 12" OC |
| Composite (Premium) | $45-60 | 30-50 years | Wash only | 12" OC |
| PVC/Vinyl | $50-70 | 50+ years | Wash only | 12-16" OC |
Authority References
Our calculations are based on guidelines and standards from these authoritative sources:
- American Wood Council (AWC) — DCA6 — Prescriptive Residential Wood Deck Construction Guide. Learn more
- International Residential Code (IRC) — Section R507 — Decks. Learn more
- North American Deck and Railing Association (NADRA) — Deck Safety Guidelines. Learn more
Frequently Asked Questions
How much does a deck cost?
Pressure-treated wood: $15-$30/sq ft. Composite: $30-$45/sq ft. A 16x12 deck costs $2,880-$7,200.
What spacing should deck joists be?
Standard: 16" OC for wood. 12" OC for composite. 24" only for 2x6 boards.