How to calculate it
Count rows across the deck width using actual board width plus gap. Determine whole stock lengths required per row, then add a cutting allowance.
Worked example
For a deck 16 ft long by 12 ft wide, 5.5 in boards and 1/8 in gaps, the width supports about 26 rows. If boards are 12 ft stock lengths, each 16 ft row needs two boards before any offcut reuse.
Before you order
- Actual board width can differ from the nominal name on the product.
- This is a simplified material purchase count and does not optimize cuts across rows.
- Deck structure, railings, footings, flashing, permits and span tables require separate design.
Frequently asked questions
Does the estimate include joists and posts?
No, this calculator estimates decking surface boards only.
What about staggered joints?
The model assumes a simple row-by-row layout. A detailed cutting and joint plan may use a different number of boards.
Can I use composite decking?
Yes, when the dimensions and gap match that product’s installation instructions.
Sources & assumptions
Geometry-based estimate. Your product specifications and supplier instructions take priority.
Calculator formulas and explanations prepared for RenovationBinder, 2026-10-15.