Deck Board Calculator
Find how many deck boards you need for your project. Calculates proper gaps, total board feet, and material cost estimates.
Length of deck (direction boards run)
Width of deck (distance between joists)
Nominal size determines coverage width
Standard board length
Typical gap is 1/8" (0.125") for pressure treated, 0 for composite
Material affects gap spacing and cost
How boards will be laid
Add extra for cuts and mistakes
How do I calculate deck board spacing?
Deck boards naturally expand and contract with moisture. Pressure treated lumber needs 1/8" gaps, composite decking typically 1/4" to 3/8" gaps (check manufacturer specs), and hardwood decking 1/16" to 1/8". The calculator uses 1/8" (0.125") as the default which works for most pressure treated decks.
How many deck boards do I need?
Measure the deck width and divide by the board width plus gap. Example: 12 wide deck with 5.5" boards and 1/8" gaps = 12 / (5.625/12) = 12 / 0.46875 = 25.6 boards. Always round up and add 10-15% for waste.
Should I use 2×6 or 5/4×6 deck boards?
5/4×6 boards (actual 1" × 5.5") are designed for decking and resist warping better than 2×6 (actual 1.5" × 5.5"). Most pros prefer 5/4×6 for decks 16" on center joists. Use 2×6 only when joists are 24" on center or for commercial applications.
How do I estimate deck board cost?
Multiply total board feet by price per linear foot. Board feet = (board width in feet) × (board length) × (number of boards). Pressure treated boards cost $1.25-1.75/linear foot, cedar $3.50-4.50, composite $3.50-8.00. Add about $0.50-1.00/board for hidden clips or screws.