Deck Boards Calculator
Estimate decking boards and total linear feet for a deck surface. Assumes 5.5 inch wide boards in 12 ft lengths and adds 10% for waste; adjust to your stock.
Deck Boards calculator
How it's calculated: Deck area in sq ft ÷ board width in feet (5.5 in ÷ 12) = linear feet of decking; add 10% waste and divide by the 12 ft board length, rounding up.
How to estimate deck boards
- This counts the deck surface only. Joists, beams, posts and fasteners are separate.
- Account for a ~1/8 to 1/4 inch gap between boards for drainage; the 10% waste covers cuts and that spacing.
- Composite and hardwood decking cost far more per board than pressure-treated pine - set your local price above.
- Buy board lengths that match the deck where you can - a 12 ft board across a 12 ft deck means no butt joints to stagger.
- Composite decking usually needs tighter joist spacing than wood, especially on diagonals - check your product's span chart before counting on existing framing.
Frequently asked questions
How many deck boards do I need?
Divide the deck area by the coverage of one board (width times length), then add ~10% for waste and gaps.
How many boards does a deck actually take?
Work from area: a 192 sq ft deck, for example, needs roughly 420 linear feet of 5.5-inch decking - about 39 twelve-foot boards after 10% waste.
What gap should I leave between boards?
About 1/8 to 1/4 inch for drainage and debris. Wet pressure-treated boards are often laid nearly tight because they shrink as they dry; kiln-dried and composite get gapped per the spec.
Which way do deck boards run?
Always perpendicular to the joists - the framing direction decides it. If you want a diagonal or a different direction, the joist layout (and sometimes spacing) has to be planned for it.
Is composite worth the extra cost?
Composite boards cost several times more than pressure-treated pine up front but skip the sand-and-stain cycle. Over a deck's life the gap narrows; if you would pay someone to refinish wood every few years, composite often wins.