Screw Size Selector
What size screw do you need?It comes down to three things: the job, how thick the material is, and whether the screw will ever get wet. A 5/4 deck board wants a #10 × 2-1/2″ coarse-thread screw with an ACQ-rated coating. The same length in a cabinet carcass would blow straight through the back panel.
The selector below asks for your project and material thickness, then returns the gauge, length, pilot hole, clearance hole, countersink, torque and coating — plus how many screws the job needs. If you would rather read the numbers off a chart, they are further down: screw size by project, gauge to diameter, and which coating survives treated lumber.
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Screw Size Selector
Pick your project and material thickness — get the exact screw type, gauge, length, pilot hole, torque, and where to buy.
Pick your application and material thickness to get your screw specification instantly.
Screw Size Chart by Project
The screw type is decided by the job before the size is. These are the defaults the selector uses — adjust the length for your actual material thickness. For the full gauge-by-gauge breakdown see the screw size chart.
| Project | Screw Type | Gauge | Drive | Typical Length |
|---|---|---|---|---|
| Decking | Deck / construction | #10 | T25 star | 2-1/2" to 3-1/2" |
| Drywall | Coarse thread (W-type) | #6 | #2 Phillips | 1-1/4" to 1-5/8" |
| Cabinets | Cabinet, fine thread | #8 | #2 Phillips | 2" to 3" |
| Framing | Structural screw | 5/16" | T30 star | 3" to 3-1/2" |
| Plywood / sheathing | Wood screw, coarse | #8 | #2 Phillips or T20 | 1-1/2" to 2-1/2" |
| Sheet metal | Self-drilling (Tek) | #8 SMS | #2 Phillips | 1/2" to 1" |
Screw Gauge to Diameter
Screw gauge is a number, not a measurement — it describes the shank diameter. Bigger number, thicker screw. Pilot and clearance holes are both sized off this diameter, which is why the same gauge behaves differently in oak than in pine. Full pilot hole numbers are in the pilot hole size chart.
| Gauge | Shank Dia. | Clearance Hole | Countersink | Common Use |
|---|---|---|---|---|
| #6 | 0.138" | 9/64" | 3/8" | Drywall, trim, light hardware |
| #8 | 0.164" | 11/64" | 7/16" | Cabinets, plywood, general woodwork |
| #10 | 0.190" | 3/16" | 1/2" | Decking, heavier framing connections |
| #12 | 0.216" | 7/32" | 9/16" | Ledger boards, heavy brackets |
| 1/4" | 0.250" | 17/64" | 5/8" | Lag-scale connections |
| 5/16" | 0.3125" | 21/64" | 3/4" | Structural screws, timber framing |
Screw Coating for Treated Lumber & Exterior
ACQ and CA pressure-treated lumber is corrosive to plain steel. An electroplated zinc screw can fail in a single season outdoors. This is the one spec people skip, and it is the one that brings the deck down — more detail in the screw coating guide.
| Application | Interior | Exterior / Treated |
|---|---|---|
| Decking | Galvanized or coated | ACQ-rated hot-dip galvanized or 316 stainless |
| Framing | Zinc or ACQ-rated | ACQ-rated or hot-dip galvanized (ZMAX) |
| Plywood / sheathing | E-coated or zinc plated | ACQ-rated or stainless |
| Cabinets | Zinc or nickel plated | Stainless or exterior-rated |
| Sheet metal | Zinc chromate or stainless | Stainless Type 410 or 304 |
Electroplated zinc is not adequate for ground contact or ACQ lumber. When in doubt outdoors, stainless is the screw you do not have to think about again.
Frequently Asked Questions
What size screw do I need for deck boards?
For 5/4 inch deck boards (1 inch actual thickness) into pressure-treated joists, use #10 x 2-1/2 inch or 3 inch deck screws. For 2x6 deck boards, use #10 x 3 inch screws. Always use stainless steel, hot-dipped galvanized, or coated screws rated for ACQ-treated lumber to prevent corrosion.
What pilot hole size do I need for wood screws?
Pilot hole size depends on screw gauge and wood species. For a number 8 screw in hardwood (oak, maple), use a 7/64 inch pilot bit. In softwood (pine, fir), use 5/32 inch. The pilot hole should be slightly smaller than the screw shank to allow thread engagement while preventing splitting.
What is the difference between structural screws and regular wood screws?
Structural screws (like GRK RSS or Simpson SDS) are engineered fasteners rated for structural connections - deck ledgers, joist hangers, post bases, and beam connections. They are stronger, harder, and listed in ICC-ES ESR reports with specific load values. Regular wood screws are for non-structural applications only.
How long should screws be for framing?
Screw length for framing should penetrate at least 1 inch into the receiving member. For 2x lumber face-screwing: use 3 inch screws to attach through one piece and into another. For toe-screwing: use 3-1/2 inch screws at 45 degrees. For LVL and engineered lumber, follow manufacturer specifications.
Do I need different screws for pressure-treated lumber?
Yes - pressure-treated lumber (especially ACQ and CA treated) is highly corrosive to standard steel fasteners. Use hot-dipped galvanized (HDG), stainless steel 304 or 316, or coated screws specifically rated for treated lumber. Electroplated zinc screws are not adequate for ground contact or ACQ lumber.