Deck Material Calculator
Board rows = deck width ÷ (board width + gap), rounded up: a 16 × 12 ft deck in 5.5 in boards with 1/8 in gaps takes 26 rows of 16 ft boards, or 29 boards with 10% extra.
Example: replace these measurements
Your material list
29 deck surface boards
29 deck surface boards
192 sq ft measured
Your shopping list
- 29 deck surface boards
Quantities and package details
- Board rows
- 26
- Stock pieces per row
- 1
- Base boards / extra boards
- 26 / 3
- Fasteners before spares
- 676
- Railing sections from plan
- Enter both measurements
Surface boards only. Framing, railing, stairs and footings are separate.
The calculation
- ceil((12 + 0.010417) ÷ (0.458333 + 0.010417)) = 26
- ceil(26 × 1 × (1 + 10/100)) = 29
Common questions
How many deck boards do I need?
Divide the deck width across the boards by the board face plus the gap to get the rows, then work out how many stock lengths each row needs. The calculator buys a whole board for every piece and adds your extra.
What gap should I leave between deck boards?
The gap in your decking maker’s instructions; wood and composite boards differ. The calculator starts at 1/8 inch as an example.
How many screws or clips do I need?
Fasteners at every joist each board crosses. Enter the count per crossing from your fastening instructions; hidden clips often use a different count from face screws.
How to plan the quantity
Choose the direction the boards run. The width across the boards determines the number of rows; the distance along them determines the stock pieces in each row.
The result allows a whole stock board for each piece, then adds your extra percentage. It does not reuse offcuts across rows. A long row with a seam needs framing and fasteners at that joint.
Joist spacing is taken from your framing plan. Fastening points multiply board rows by support lines and the number of fasteners you enter. Proprietary clips and border boards may use different details.
Before you order
- This covers deck surface boards. It does not size beams, joists, posts, footings or connections.
- Stairs, railing, picture-frame borders and diagonal layouts need their own cut and support plan.
Have prices moved?
Lumber cost 7.6% more in August 2026 than a year earlier (Bureau of Labor Statistics producer price index, preliminary).
What owners paid: the typical porch, deck, patio and terrace job cost $4,750 in the 2023 Census survey.
Newer monthly figures may be out: these were checked on .
Plan the work as well as the order: How to build a deck: permit, footings, framing and boards.
Before ordering, read the guide: How many deck boards do I need? Boards, gaps and screws. Or choose another calculator.