Deck Material Calculator
Deck boards, joists, footings, and screws from your deck dimensions — with board length, joist spacing, and waste factored in.
A deck is one of the most popular DIY projects and one of the easiest to under-buy, because the boards, joists, and footings all count differently. Enter the deck's dimensions and this calculator returns the deck boards (at your chosen length, with waste), the field joists at your spacing, a footing-grid estimate, and the screws.
This covers field material. For the footings themselves, size the concrete with the Concrete Calculator, confirm the surface area with the Square Footage Calculator, and fold the lumber into your Renovation Budget. Planning the space first is in the outdoor patio planning guide.
FAQ
- How many deck boards do I need?
- Divide the deck width by the board face width plus the gap to get the number of rows, multiply by the deck length for linear feet, add ~10% waste, then divide by your board length. This calculator does all of that and rounds up to whole boards.
- What does the calculator NOT include?
- It estimates field material — decking, field joists, footings, and screws. It does not include the ledger board, rim/band joists, beams, post anchors, footing concrete, stairs, or railing. Add those separately so you don't under-order structural lumber.
- How far apart should deck joists be?
- 16 inches on center is standard. Use 12 inches for a stiffer feel or diagonal decking, and 24 inches only where your decking and local code allow it. The joist count includes a closing joist at each end.
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