Pilot hole too big or too small? Here's what to do

Last updated: July 12, 2026

A pilot hole only helps when it's the right size. Too small and the screw fights you, splits the board, or snaps; too big and it won't grip and just spins. Both are fixable in a couple of minutes. Here's what to do for each — and how to get the size right the first time.

Quick fix: Too small — the screw's hard to drive and may split or snap; redrill one bit size up to the correct size. Too big — the screw won't grip and spins; pack the hole with glue and toothpicks or a dowel, or use a bigger screw. Get it right first with the pilot-hole finder.

First: too big, too small, or too shallow?

A pilot hole has two dimensions — diameter (how wide) and depth (how deep) — and almost every problem is about the diameter being wrong. A too-narrow hole makes the screw hard to drive; a too-wide hole makes it spin without gripping. Depth matters less often, but a hole that's too shallow causes its own trouble. Figure out which one you've got, then jump to the fix.

Pilot hole too small (diameter)

If the pilot is too narrow for the screw, the screw has to force the extra wood aside as it drives. You'll feel it bind and drive hard — and that resistance causes three problems: it can split the board (the very thing the pilot was meant to prevent), it can snap the screw head or shear the shank clean off (especially with brass or smaller screws), and the strain makes the driver cam out and strip the head.

The fix is simple: redrill the hole to the correct size. Step up one bit at a time until you reach the right diameter for your screw and wood — it's easy to enlarge an existing hole, so sneak up on it rather than jumping straight to a big bit. Then drive the screw; it should go in firmly but without a fight.

Pilot hole too big (diameter)

If the pilot is wider than the screw's root (the solid core under the threads), the threads have nothing to bite and the screw spins without pulling tight — or strips straight out. This is exactly the stripped-hole problem, and the repairs are the same: give the threads fresh wood.

• Matchsticks or toothpicks + wood glue. Pack the hole with glue-coated toothpicks, snap them flush, let it cure, and redrive. Good for light and medium loads.
• A wooden dowel or golf tee. For a bigger or load-bearing hole, glue in a dowel, let it set, then drill a fresh pilot. The strongest fix.
• Go up a screw size. A thicker or longer screw can reach into fresh wood the oversized hole didn't touch.
• Wood filler or epoxy. For non-structural spots, packs the hole and holds once cured — not for heavy loads.
• Relocate. When strength matters, move the screw slightly into solid wood.

Pilot hole too shallow or too short (depth)

If the pilot doesn't go deep enough, the screw runs out of pre-drilled hole partway in. From there it either bottoms out against solid wood and stalls with the head standing proud, or it forces its own way the rest of the way and splits or snaps at the bottom. Drill the pilot at least as deep as the screw will go — a little deeper is fine. For long screws, wrap a piece of tape around the bit at the right depth so you know when to stop.

Too big or too small for a wall anchor

The same logic applies to the hole for a drywall or masonry anchor, and it trips people up just as often. Too big and the anchor spins in the hole instead of seating — it won't grip and pulls straight out under load. Too small and the anchor won't go in, or it distorts. Match the drill bit to the size the anchor's packaging specifies, not to the screw — the anchor, not the screw, sets the hole size here.

Getting it right the first time

The correct pilot is sized to the screw's root (core) diameter, so the threads still bite but the wood isn't forced apart — and it's slightly larger in hardwood than in softwood. That's the part people guess at and get wrong, so we built a tool for it: pick your screw gauge and what you're drilling into, and it gives you the exact bit as a fraction and in millimetres.

Two neighbours worth a look: if a too-small pilot is splitting your boards, see how to keep wood from splitting; if a too-big pilot left the screw spinning, why your screw keeps stripping covers the repair in full.

The bottom line

Too small: redrill up to the correct diameter and the screw drives clean. Too big: pack the hole with glue and toothpicks or a dowel, or move up a screw size. Too shallow: drill deeper, to the screw's full length. And to skip the do-over next time, size the pilot to the screw's core with the finder before you drill.