Decking Calculator
Use this free Decking Calculator to estimate deck area, decking boards, material cost, and waste for a deck project.
How This Decking Calculator Works
This calculator estimates deck area, decking boards, and material cost. Enter deck length and width, choose a decking material, and add a waste percentage for cuts and installation adjustments.
Decking Calculator Formula
Deck Area = Deck Length × Deck Width
Adjusted Area = Deck Area × (1 + Waste %)
Estimated Boards = Adjusted Area ÷ Board Coverage
Estimated Cost = Adjusted Area × Material Cost Per Sq Ft
Example Calculation
For a 20 ft by 12 ft deck using composite decking with 10% waste:
- Deck area: 20 × 12 = 240 sq ft
- Adjusted area: 264 sq ft
- Estimated boards: about 40 boards
- Average material cost: 264 × $10 = $2,640
Average Decking Cost by Material
| Decking Material | Estimated Cost / sq ft |
|---|---|
| Pressure-Treated Wood | $3.00 - $6.00 |
| Cedar Decking | $6.00 - $10.00 |
| Composite Decking | $8.00 - $14.00 |
| PVC Decking | $10.00 - $16.00 |
| Premium Hardwood | $12.00 - $25.00+ |
FAQ
How do I calculate deck area?
Multiply deck length by deck width. For example, a 20 ft by 12 ft deck has an area of 240 square feet.
How many decking boards do I need?
This calculator estimates board quantity using a common 5.5-inch wide by 12-foot long deck board, which covers about 5.5 square feet.
Should I add waste for decking?
Yes. Most deck projects include 10% waste for cuts, trimming, mistakes, and board spacing.
Is this an exact contractor quote?
No. This calculator gives a rough planning estimate. Actual cost depends on framing, railing, stairs, fasteners, labor, permits, and local pricing.