Deck Screw Calculator

Board courses (whole count). Count the parallel board courses that cross the supporting framing. A course is a row of decking, not necessarily one purchased board. Estimate extra fastening at butt joints, borders and other details separately.

Joist/support intersections per course. Count the joists or other supports crossed by one board course. Each crossing is a fastening location. Use the actual framing layout; this field does not determine adequate joist spacing or structural support.

Fasteners per intersection. Enter the screws required at each board-to-support crossing for the selected decking system. Obtain that number from the approved installation detail or product instructions. Hidden fasteners or different edge details may require a separate count.

Screws per box. Enter the actual number of screws in one box. Use the package count rather than its weight unless the supplier provides a reliable conversion. The result rounds up to complete boxes.

Allowance (%). Enter the percentage you want to add for cutting, handling loss or other conditions specific to this work. Apply it to the measured quantity rather than enlarging the measurements as well. The suggested value is editable, not a universal recommendation; enter zero when no allowance is needed.

Net screws come from board courses, support crossings and fasteners at each crossing. Required screws include the allowance and are rounded to whole fasteners; boxes round that same demand to complete packages. This does not count special connections or establish an approved fastening schedule.

Net screws = board courses × supporting intersections per course × fasteners per intersection. Apply allowance, then round up screws and boxes separately from the unrounded requirement.

Worked example: 22 courses × 11 supports × 2 screws = 484 screws. With 10% allowance, purchase at least 533 screws, or 3 boxes of 200.

Assumes identical support count per course. Butt joints, doubled supports, borders, stairs, hidden clips and structural connectors require separate counts. This is not a fastening specification.