The screw label tells you two things — gauge and length — and the material tells you which screw to reach for. Here's how to read a screw, how to measure one, and what to use where.
A label like #8 × 1-1/2″ means gauge #8 (the shaft diameter) and 1-1/2″ long. Gauge sets how thick and strong it is; length sets how deep it anchors.
This trips people up. The rule depends on the head: if it sits flush, you include the head; if it sits on top, you don't.
Match the screw to what you're driving into — the wrong type strips, splits, or works loose. Sizes below are common starting points, not hard rules.
| Material | Screw type | Common size | Key note |
|---|---|---|---|
| Wood | Coarse-thread wood screw | #6–#10 · 1″–3″ | Longer for load-bearing. Pilot-drill hardwood and anything near an edge. |
| Drywall | Bugle-head drywall screw | #6–#8 · 1¼″–2″ | Anchor into a stud, or use a wall anchor — drywall alone won't hold weight. |
| Sheet metal | Self-tapping / sheet-metal screw | #8–#14 | Fine threads bite thin metal. Drill a pilot hole for thicker gauge. |
| Masonry concrete / brick | Masonry screw + anchor | ³⁄₁₆″–¼″ · 1¼″–3″ | Hammer-drill the pilot. Use an expansion anchor for heavy loads. |
| Plastic / composite | Coarse-thread wood or sheet-metal screw | #6–#10 | Drive slowly and pilot-drill to avoid cracking. |
A handful of sizes cover most jobs. If you're stocking a kit, #6, #8 and #10 in 1″–2″ lengths (plus a few anchors) handle the majority of household work.
| Size | Typical use | Note |
|---|---|---|
| #6 × 1″ | Trim, hinges, light wood joinery | Indoor, low-load work. |
| #8 × 1¼″ | Cabinets, furniture assembly | The everyday interior screw — most common size. |
| #10 × 1½″ | Drywall into studs, heavier frames | Strong hold without splitting the stud. |
| #12 × 2″ | Metal brackets, structural hardware | Where you need extra grip. |
| #14 × 2½″ | Decking, outdoor fixings | Pair with a corrosion-resistant coating. |
| M6 × 16 mm | Automotive, light machinery | Metric — imported or precision builds. |
| M4 × 10 mm | Electronics, appliance panels | Small, fine threading. |
Exact diameters for each gauge (and pilot-hole sizes) are on the wood screw chart. These are practical starting points — always match thread type and length to your actual material and load.
The first number is the gauge — the shaft diameter (#8 = 0.164″). The second is the length, 1-1/2″. So "#8 × 1-1/2″" is a medium screw, an inch and a half long.
#10. With gauge numbers, higher = thicker. Each step up adds 0.013″ to the diameter, so a #10 (0.190″) is noticeably beefier — and stronger — than a #8 (0.164″).
It'll go in, but it's not ideal: sheet-metal screws have fine threads that don't grip wood fibres well and can work loose. Use a coarse-thread wood screw for a lasting hold.
#8 × 1-1/4″. It's the default for furniture, cabinets, and light framing — if you keep one box of screws in the drawer, make it this one.
Yes. Coarse threads grip soft materials (softwood, drywall, plastic); fine threads suit metal and dense hardwood where you want a tighter, cleaner bite. Match the thread to the material.