what size drill bit for 8 screw

For a standard #8 screw, the typical drill bit sizes are:

Pilot hole in wood (softwood): 7/64 inch
Pilot hole in wood (hardwood): 1/8 inch
Pilot hole in metal: 11/64 inch (commonly recommended so the screw can cut properly without stripping)

If you meant 8 mm screw (metric) instead of “#8”:

For a through-hole (the screw passes freely through): use an 8 mm bit.
For an anchor/plug rated M8 in masonry: check the plug, but many take a 10 mm masonry bit so the plastic anchor can expand.

The pilot hole is usually about the size of the screw’s shank (the solid core without the threads) so the threads still bite firmly.
Softer materials can use a slightly smaller pilot hole; harder materials need a bit larger pilot to avoid splitting or breaking screws.
Metal needs a closer fit (like 11/64 inch for #8) so threads form cleanly without over-stressing the screw.

Confirm what you actually have: “#8” wood/metal screw (imperial) or 8 mm screw (metric) on the box.
Decide material: softwood, hardwood, metal, or wall with anchor.
Pick from this mini‑cheat sheet:
- #8 wood screw → 7/64" (softwood) or 1/8" (hardwood) pilot.
- #8 screw into metal → 11/64" bit.
- 8 mm screw through a clearance hole → 8 mm bit.
- M8 anchor in masonry → normally 10 mm masonry bit, but always follow what’s printed on the anchor.

If you tell me exactly: “#8 wood screw into pine” or “8 mm screw with wall plug in brick,” I can give a one‑line, very specific size recommendation.