You measure twice, drill once, and then the anchor spins uselessly in a hole that’s too big — or won’t go in at all because the hole is too small. Hanging a curtain rod, a floating shelf, or a TV mount shouldn’t feel like guesswork, but the wrong drill bit is one of the most common reasons wall anchors strip out, spin freely, or crack the drywall around them. Renters and small-space homeowners feel this the most, since you usually get one clean shot at a hole before you’re stuck patching and repainting.
The good news: matching a drill bit to an anchor or screw follows a short list of standard sizes used consistently across hardware brands. Below is a complete drill bit size chart for the anchors and screws you’ll actually use at home — plastic wall anchors, toggle bolts, molly bolts, masonry anchors, and wood screw pilot holes — along with the approximate weight limit each one can safely hold in drywall, plaster, brick, or concrete. Match your anchor package to the chart, and you’ll drill the right hole the first time, every time.
Quick Facts: Drill Bit Sizes at a Glance
| Anchor/Screw Type | Drill Bit Size | Best Wall Material | Weight Limit (per anchor) |
|---|---|---|---|
| Small plastic anchor | 3/16 in (4.8 mm) | Drywall, plaster | Up to 15 lbs |
| Medium plastic anchor | 1/4 in (6.4 mm) | Drywall | 20–25 lbs |
| Large plastic anchor | 5/16 in (8 mm) | Drywall over studs | 30–35 lbs |
| Self-drilling anchor | None, or 3/16 in for dense plaster | Drywall | 50–75 lbs |
| 1/8 in toggle bolt | 3/8 in (9.5 mm) | Drywall, plaster | Up to 20 lbs |
| 1/4 in toggle bolt (spring-wing) | 3/4 in (19 mm) | Drywall | Up to 50 lbs |
| Plastic sleeve masonry anchor | 5/16–3/8 in (8–9.5 mm) | Brick, block, concrete | Follow the manufacturer’s stated rating on the package |
| 3/8 in wedge anchor | 3/8 in (9.5 mm) | Solid concrete | 1,000+ lbs (shear) |
| #8 wood screw pilot hole | 3/32 in (softwood), 1/8 in (hardwood); 11/64 in = shank/clearance hole | Wood stud, furniture | Rated by screw, not anchor |
Weight limits assume a single anchor installed correctly in sound, undamaged wall material. Always check the manufacturer’s packaging for exact ratings, since formulations and designs vary between brands (for reference, see Simpson Strong-Tie’s official anchor specification sheets). A pilot hole should always be smaller than the outer diameter of the screw’s threads, or the threads won’t have anything to grip.
What Drill Bit Size Do You Need? The Short Answer
For most household jobs, the drill bit size should match the diameter of the anchor’s body — not the screw that goes into it. A standard plastic drywall anchor sized for a #8–#10 screw typically needs a 1/4-inch (6.4 mm) bit; a 1/4-inch spring-wing toggle bolt needs a 3/4-inch (19 mm) hole (metal snap toggles use 1/2 inch); and a 3/8-inch masonry sleeve anchor needs a 3/8-inch masonry bit in solid concrete. Drilling even 1/16 inch oversized can cut an anchor’s holding power dramatically, since the anchor body no longer expands tightly against the surrounding material. When in doubt, check the anchor’s packaging first — reputable brands print the exact recommended bit size right on the label, and that’s more reliable than any general chart, including this one.
How to Read Drill Bit Numbers, Letters, and Fractions
Drill bits are sold in three main systems, and mixing them up is a common source of confusion. Fractional-inch bits (1/16 in, 1/8 in, 3/16 in, up through 1/2 in and beyond) are the most common for home projects and are what most anchor charts reference. Wire-gauge bits (numbered #1 through #60, smallest to largest) and letter bits (A through Z, smallest to largest) are used mostly for precise machine screw pilot holes and are rarely needed for wall anchors. Metric bits are sized in millimeters and are common on imported hardware; 6 mm is roughly 1/4 inch, and 8 mm is roughly 5/16 inch.
- A basic 29-piece fractional bit set covers 1/16 in to 1/2 in in 1/32-inch steps, which handles nearly every wall anchor listed in this guide.
- Masonry bits look similar to standard twist bits but have a wider, flat carbide tip; use these only in brick, block, or concrete, since they won’t cut cleanly through wood or metal. Always wear safety glasses and an N95/P2 dust mask when drilling brick, block, or concrete, and vacuum the dust rather than blowing it out.
- If a package lists a bit size as a range (for example, “5/16–3/8 in”), start with the smaller size, test the anchor by hand, and step up only if it won’t seat without force. It’s easier to enlarge a hole than to patch one that’s already too big.
- Metric and fractional bits are close but not identical — a 6 mm bit is slightly smaller than 1/4 inch. For anchors with tight tolerances, like toggle bolts, stick to whichever unit the packaging specifies.
Drywall, Plaster, Brick, and Concrete: Why the Wall Material Changes Everything
The same anchor size can behave completely differently depending on what’s behind your paint. Drywall and plaster are soft enough that plastic anchors and self-drilling anchors grip mainly by friction and slight expansion, which is why oversized holes hurt holding power so much. Brick and concrete block are denser but often hollow or crumbly at the surface, so sleeve anchors rely on the plastic sleeve expanding against solid material deeper in the hole — this is also why masonry bits need a slower drill speed and steady, even pressure rather than force. Solid poured concrete is the strongest base of all, which is why wedge anchors rated for over 1,000 pounds of shear strength are only accurate when drilled into concrete without air pockets or rebar in the way.
Before drilling into brick or concrete, it helps to tap the surface lightly with the tip of the bit; a solid, consistent sound means solid material, while a hollow or crumbly feel usually means you’ve hit a mortar joint or a weaker block cavity that won’t hold an anchor as well.
Common Mistakes That Ruin a Wall Anchor Installation
Most anchor failures trace back to one of a few avoidable errors:
- Drilling the hole too large. This is the single most common mistake — always match the bit to the anchor body, not the screw.
- Skipping the stud finder. Heavy items like TV mounts and shelves hold far more weight driven into a stud than any drywall anchor can offer, even a rated one.
- Overtightening plastic anchors. Cranking the screw too far can crack or split the anchor body, especially in older, drier drywall.
- Using a wood bit on masonry. Standard twist bits dull quickly against brick and concrete and won’t drill a clean, round hole; use a carbide-tipped masonry bit instead.
- Ignoring the weight rating. A single small plastic anchor rated for 15 pounds won’t safely hold a mirror or shelf loaded with books — use toggle bolts or find a stud for anything heavier.
Wood Screw Pilot Hole Size Chart
Pilot hole diameter depends on the screw size and the wood type — softwood needs a slightly smaller pilot hole than hardwood because the fibers compress more easily. The pilot hole should always be smaller than the outer diameter of the screw’s threads.
| Screw Size | Pilot Hole (Softwood) | Pilot Hole (Hardwood) |
|---|---|---|
| #6 | 1/16 in | 5/64 in |
| #8 | 3/32 in | 1/8 in |
| #10 | 7/64 in | 9/64 in |
| #12 | 1/8 in | 5/32 in |
Frequently Asked Questions
What size drill bit do I use for a standard plastic wall anchor?
Most plastic wall anchors sized for a #8–#10 screw need a 1/4-inch (6.4 mm) bit. Smaller anchors rated for lighter loads often use a 3/16-inch bit, so check the size printed on the anchor packaging before drilling.
Do toggle bolts need a bigger hole than plastic anchors?
Yes. Toggle bolts require a hole large enough for the folded metal wings to pass through, so a 1/4-inch spring-wing toggle bolt needs a 3/4-inch hole — far larger than the bolt itself, while metal snap-toggle versions use a 1/2-inch hole.
Can I use a regular drill bit on brick or concrete?
No. Standard twist bits dull almost immediately against masonry. Use a carbide-tipped masonry bit, which has a wider, flatter tip built to grind through brick, block, or concrete without breaking down.
What happens if I drill the hole too big for an anchor?
The anchor won’t expand tightly against the surrounding material, which sharply reduces its holding power and can cause it to spin freely or pull straight out under load. When a hole ends up oversized, switch to the next size up of anchor rather than trying to force a smaller one to grip.
Is it better to go into a stud instead of using a wall anchor?
For anything heavy — TV mounts, full-length mirrors, or loaded shelving — yes. A screw driven directly into a wood stud almost always holds more weight than even a heavy-duty anchor in drywall alone. Use a stud finder first, and reserve anchors for lighter items or spots where a stud isn’t available.
Reviewed and edited by Jason Paik. Spotted an error? Tell us — we verify and correct. See how we create content.