Deck Board Calculator
Find out exactly how many deck boards, screws, and joists your project needs. Accounts for board width, gap spacing, and a waste allowance.
Ad
Ad
How to calculate deck boards
Divide your deck width by the board face width plus the gap to get the number of rows. Multiply rows by the deck length for total linear feet, add 10–15% for waste and off-cuts, then divide by the length of the boards you’re buying.
How many screws per deck board?
For face-screwed decking, use two screws at every joist crossing. With joists 16" on center that’s about 350 screws per 100 sq ft. Hidden fastener systems use one clip per board at each joist instead.
Frequently asked questions
- Why add a waste percentage?
- Cuts, miters, defects, and diagonal layouts all create scrap. 10% is typical; use 15% for angled or herringbone patterns.
- What gap should I leave?
- 3/16" is common for dry pressure-treated and composite boards. Wet pressure-treated lumber shrinks, so gap them tighter (1/8").
Next steps
- Deck Cost Calculator — total project price.
- Footing & Concrete Calculator — posts and concrete.
- Stairs Calculator — risers, treads, stringers.