Wood Screw Quantity Calculator
Screws are sold by the box and weight, not the piece, so you need a number that survives the round trip to the hardware store. This counts structural fasteners at standard spacing and converts to boxes.
Results
Enter your measurements above and press Calculate.
Buy the materials this project needs
WoodCalc gives you the shopping list. Pick the items below to source decking boards, framing lumber, fasteners, and finishes at current prices.
Prices and availability change; we may earn a commission on purchases made through these links.
Questions people ask
How many screws for decking?
Two screws per board at each joist crossing is the structural minimum. For a 16×20 deck with 1×6 decking at 16 inch joist spacing, that works out to roughly 300 structural screws plus the framing and railing connections.
What size screws for decking?
2½ to 3 inch structural screws rated for pressure treated lumber. Ordinary drywall screws have a weak head that strips in treated wood. Use screws specifically labeled for exterior or ground contact.
Do galvanized screws rust in pressure treated lumber?
Modern ACQ treated lumber is far less corrosive than the old CCA era, and standard hot-dip galvanized screws perform acceptably. In coastal or wet conditions use stainless or manufacturer-coated structural screws.
Screws or nails for framing?
Screws have three to ten times the withdrawal strength of nails, which matters on decks and any structure that may flex. Many inspectors now require screws for decks and outdoor framing. Nails remain fine for interior wall plates.
Related tools
WoodCalc is a free independent tool. We may earn a commission when you buy through links on this page. Our recommendations are not influenced by any manufacturer or retailer. See our affiliate disclosure.