Decking Calculator
Calculate decking material quantities for composite and pressure-treated deck surfaces, with waste allowance.
Formula & Explanation
The decking calculator computes how many decking boards are needed for your deck surface. Formula: Boards = (Deck Area) ÷ [(Board Width + Gap) × Board Length] × (1 + Waste%) Board coverage is calculated as the percentage of the deck area that boards actually cover. With gaps included, the effective width of each board is larger than its actual dimension, accounting for spacing requirements. Waste percentage protects against cutting losses and future repairs.
Assumptions
- •Board width and gap are in inches; deck dimensions in feet
- •Waste allowance is 5-15% for linear layouts, 15-25% for diagonal patterns
- •Gap requirement varies: composite typically 1/16"-1/8", pressure-treated 1/8"-1/4"
- •Coverage calculation assumes optimal board placement with minimal waste
- •Boards must fit within deck dimensions; cutting not optimized
Example Calculation
A 20x15 deck with 5.5" composite boards requires 49 boards with 8% waste allowance for cuts.
Inputs
Results
Decking Material Comparison and Board Coverage
| material | width | weight | price | maintenance |
|---|---|---|---|---|
| Pressure-treated 2x6 | 5.5" | 2.8 lbs/sqft | $3-6/sqft | High |
| Cedar 2x6 | 5.5" | 2.9 lbs/sqft | $8-12/sqft | High |
| Composite (solid) | 5.5" | 3.5-4 lbs/sqft | $10-15/sqft | Low |
| Composite (hollow) | 5.5" | 2.5-3 lbs/sqft | $8-12/sqft | Low |
| Azek (PVC) | 6" | 3.8 lbs/sqft | $12-18/sqft | Minimal |
| Trex Transcend | 5.5" | 3.6 lbs/sqft | $10-14/sqft | Low |
| TimberTech | 5.5" | 3.2 lbs/sqft | $9-13/sqft | Low |
Frequently Asked Questions
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