Deck Board Calculator
Calculate how many deck boards you need based on deck dimensions, board width, and spacing.
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How to Calculate Deck Boards
Divide deck width (in inches) by board width plus gap to get number of boards. Multiply by the number of runs if boards are shorter than deck length. Add 10% for waste and cuts.
Frequently Asked Questions
How many deck boards do I need for a 12x12 deck?
For a 12x12 foot deck using standard 5.5-inch wide boards with 1/8-inch gaps, you need approximately 26 boards at 12 feet long. With 10% waste, buy 29 boards.
What is the gap between deck boards?
Standard gap is 1/8 inch (3 mm) for wood boards and 3/16 inch (5 mm) for composite. This allows for drainage and expansion. In very humid climates, some builders use 3/16" for wood as well.
How much do deck boards cost?
Pressure-treated pine: $2-$4 per linear foot. Cedar: $4-$7 per linear foot. Composite (Trex, TimberTech): $5-$12 per linear foot. Exotic hardwood (Ipe): $8-$15 per linear foot. A 12x16 deck costs roughly $500-$2,500 in boards alone depending on material.
Should I use 12 or 16 foot deck boards?
Use the longest board that spans your deck without joints — joints are weak points and trap moisture. For a 14-foot deck, use 16-foot boards and trim. If your deck is wider than available board lengths, stagger joints over joists and offset them row to row.
How many screws do I need for deck boards?
Use 2 screws per board at each joist. With joists at 16 inches on center, a 12-foot board crosses about 10 joists = 20 screws per board. A typical 12x16 deck needs roughly 600-750 screws (about 7-8 lbs of 3-inch deck screws).