Deck Board Estimator
Calculate how many deck boards you need — including waste allowance.
Deck dimensions
Board size
Running direction
Choose the direction boards will run across your deck.
Your estimate
Boards to buy
—
boards
Deck area
—
sq ft
Linear footage
—
lin ft
Rows of boards—
Boards per row (— ft boards)—
Boards before waste—
Waste allowance added—
Total boards (rounded up)—
How to use this deck board estimator
Enter your deck's length and width in feet, choose your board size and spacing, then set a waste allowance based on how complex your deck layout is. A standard rectangle with boards running parallel to one edge only needs 10% waste. Diagonal layouts or curves should use 15–20%.
The calculator works out how many rows of boards span the deck, how many boards are needed per row to cover the length, then applies your waste factor and rounds up to the nearest whole board. Always buy the rounded-up number — off-cuts and defective boards are a normal part of any deck build.
Frequently asked questions
What's the standard gap between deck boards?
³⁄₁₆" (about 3/16 inch) is the most common gap. It allows for drainage and wood expansion without being wide enough to catch heels. For composite decking, follow the manufacturer's spec — typically ¼".
Should I use 2×4 or 2×6 deck boards?
2×6 boards (5.5" actual face width) are the most popular choice — they cover more area per board, reducing your joist count and install time. 2×4s are used where joists are closer together or for lighter-duty builds.
Does the calculator account for the fascia board?
No — fascia boards run along the perimeter edges and are calculated separately. Add one fascia board per exposed deck edge, typically the same profile as your decking boards.
How much waste should I add for a diagonal deck?
Use 15% for a straightforward 45° diagonal layout. Complex angles, multiple directions, or curves with a lot of trimming should use 20% or more.