Concrete Anchor Drill Bit and Hole Size Chart
Choosing the correct drill bit and hole depth is the most important step in a concrete anchor installation. An undersized hole prevents the anchor from seating properly. An oversized hole reduces holding power. This chart covers the drill bit diameter, hole depth, minimum embedment, torque values, and minimum concrete thickness for every standard concrete anchor diameter from 1/4" through 1". Bookmark this page for quick reference on your next project.
Wedge Anchor Drill Bit & Installation Chart
Wedge anchors require a hole diameter that matches the anchor diameter exactly. The hole must be drilled deeper than the minimum embedment depth to allow space for dust and anchor expansion. Always use a carbide-tipped SDS or hammer drill bit rated for concrete.
| Anchor Diameter | Drill Bit Diameter | Min. Embedment Depth | Min. Hole Depth | Torque (ft-lbs) | Min. Concrete Thickness |
|---|---|---|---|---|---|
| 1/4" | 1/4" | 1-1/8" | 1-1/2" | 4 | 2-1/4" |
| 3/8" | 3/8" | 1-1/2" | 2" | 15 | 3" |
| 1/2" | 1/2" | 2-1/4" | 2-3/4" | 40 | 4-1/2" |
| 5/8" | 5/8" | 2-3/4" | 3-1/4" | 60 | 5-1/2" |
| 3/4" | 3/4" | 3-1/4" | 3-3/4" | 80 | 6-1/2" |
| 1" | 1" | 4-1/2" | 5" | 150 | 9" |
Values based on Simpson Strong-Tie Strong-Bolt 2 (STB2) specifications. Other manufacturers may vary slightly. Always follow the anchor manufacturer’s published installation data.
Sleeve Anchor Drill Bit & Installation Chart
Sleeve anchors use a drill bit that matches the anchor body diameter. Unlike wedge anchors, sleeve anchors can be used in hollow block and brick as well as solid concrete. They offer moderate pull-out strength and are a good choice for medium-duty applications like handrails, electrical boxes, and light equipment mounting.
| Anchor Diameter | Drill Bit Diameter | Min. Embedment Depth | Min. Hole Depth | Torque (ft-lbs) | Min. Concrete Thickness |
|---|---|---|---|---|---|
| 1/4" | 1/4" | 1" | 1-3/8" | 3 - 5 | 2" |
| 3/8" | 3/8" | 1-1/2" | 1-7/8" | 10 - 15 | 3" |
| 1/2" | 1/2" | 2-1/4" | 2-5/8" | 25 - 35 | 4-1/2" |
| 5/8" | 5/8" | 2-1/2" | 3" | 40 - 55 | 5" |
| 3/4" | 3/4" | 3-1/4" | 3-3/4" | 55 - 70 | 6-1/2" |
Values based on Simpson Strong-Tie Sleeve-All (SL) specifications. Torque ranges reflect hand-tight plus additional turns. Always follow the anchor manufacturer’s published installation data.
Concrete Screw Anchor Drill Bit & Installation Chart
Concrete screw anchors (sometimes called Tapcon-style or self-tapping anchors) cut threads directly into the concrete. They require a pilot hole slightly smaller than the anchor diameter. These anchors are removable and offer fast installation without expansion force, making them ideal for close-to-edge and close spacing applications.
| Anchor Diameter | Pilot Bit Diameter | Min. Embedment Depth | Max. Embedment Depth | Min. Hole Depth | Min. Concrete Thickness |
|---|---|---|---|---|---|
| 3/16" | 5/32" | 1" | 1-3/4" | 1-1/4" | 2" |
| 1/4" | 3/16" | 1" | 1-3/4" | 1-1/4" | 2" |
| 3/8" | 5/16" | 1-1/2" | 3" | 2" | 3" |
| 1/2" | 3/8" | 2" | 3-3/4" | 2-1/2" | 4" |
| 5/8" | 1/2" | 2-1/2" | 5" | 3" | 5" |
| 3/4" | 5/8" | 2-3/4" | 6" | 3-1/2" | 6" |
Values based on Simpson Strong-Tie Titen HD (THD) large-diameter screw anchor specifications. Standard Tapcon-style (3/16" and 1/4") values are industry standard. Always follow the anchor manufacturer’s published installation data.
Key Terms & Drilling Tips
Definitions
- Embedment Depth — How deep the anchor sits inside the concrete, measured from the surface of the concrete to the bottom of the anchor. Deeper embedment generally means higher holding power.
- Hole Depth — How deep you drill the hole. This is always deeper than the embedment depth to allow room for concrete dust at the bottom of the hole.
- Minimum Concrete Thickness — The thinnest slab or wall the anchor can be used in without risk of blow-out on the back side. As a rule of thumb, this is roughly twice the embedment depth.
- Torque Value — How tight to turn the nut after the anchor is set. Over-torquing can crack the concrete or spin the anchor in the hole.
Drilling Tips
- Always use a carbide-tipped SDS-plus or SDS-max hammer drill bit rated for concrete. Standard masonry bits will dull quickly and produce oversized holes.
- Hold the drill perpendicular to the surface — an angled hole reduces holding power and can prevent the anchor from seating flush.
- After drilling, blow out the hole with compressed air or a hand pump to remove concrete dust. Dust at the bottom of the hole prevents full embedment.
- Mark the drill bit with tape at the correct hole depth so you drill consistently across all anchor locations.
- When drilling near an edge, maintain the minimum edge distance specified by the anchor manufacturer — typically 5 to 10 anchor diameters from the edge.
Frequently Asked Questions
Can I use a regular masonry bit for concrete anchors?
A standard masonry bit will technically drill into concrete, but it dulls much faster than a carbide-tipped hammer drill bit and tends to produce a slightly oversized, rougher hole. For reliable anchor performance, always use an SDS-plus or SDS-max carbide bit designed for rotary hammer drills.
What happens if I drill the hole too deep?
For wedge and sleeve anchors, a slightly deeper hole is fine — the extra space just collects dust. However, if the hole is significantly deeper than needed, the anchor may not expand against the concrete properly. For screw anchors, exceeding the maximum embedment depth can strip the threads in the concrete. Follow the hole depth values in the charts above.
Do I need a different drill bit for stainless steel anchors?
No. The drill bit is for the concrete, not the anchor. Use the same carbide-tipped bit regardless of whether the anchor is zinc plated, stainless steel, or galvanized. The drill bit diameter is determined by the anchor diameter, not the anchor material.
What is the difference between a wedge anchor and a sleeve anchor?
Wedge anchors expand at the bottom of the hole and provide the highest pull-out strength in solid concrete. They are permanent — once set, they cannot be removed without cutting them off. Sleeve anchors expand along the full length of the body and work in both solid concrete and hollow materials like block and brick. They offer moderate holding power and can be partially disassembled. For a detailed comparison, see our Concrete Anchor Selection Guide.
How do I know if my concrete is strong enough for anchoring?
Most concrete anchor specifications assume a minimum compressive strength of 2,000 to 3,000 psi. Standard structural concrete is typically 3,000 to 4,000 psi. If you are anchoring into older concrete, lightweight concrete, or concrete block, check the anchor manufacturer’s load tables for the appropriate base material. When in doubt, consult a structural engineer.
Related Resources
- Wedge Anchor Selection & Installation Guide — step-by-step installation with torque tables and material comparisons
- Concrete Anchor Selection Guide — choosing between wedge, sleeve, and screw anchors for your application
- Shop Wedge Anchors
- Shop Sleeve Anchors
- Shop All Concrete Anchors