Drill Bit Size Chart
The Drill Bit Size Chart is a technical reference tool covering drill bit size chart, drill size chart, drill bit size chart for screws, drill bit diameter chart. Use the chart below to look up values instantly. Printable and downloadable versions are available on this page.
Drill Bit Size Chart — Fractional Inches
| Drill Bit Size (Fraction) | Decimal Inches | Millimetres |
|---|---|---|
| 1/64" | 0.0156" | 0.397 mm |
| 1/32" | 0.0313" | 0.794 mm |
| 3/64" | 0.0469" | 1.191 mm |
| 1/16" | 0.0625" | 1.588 mm |
| 5/64" | 0.0781" | 1.984 mm |
| 3/32" | 0.0938" | 2.381 mm |
| 7/64" | 0.1094" | 2.778 mm |
| 1/8" | 0.1250" | 3.175 mm |
| 9/64" | 0.1406" | 3.572 mm |
| 5/32" | 0.1563" | 3.969 mm |
| 11/64" | 0.1719" | 4.366 mm |
| 3/16" | 0.1875" | 4.763 mm |
| 13/64" | 0.2031" | 5.159 mm |
| 7/32" | 0.2188" | 5.556 mm |
| 15/64" | 0.2344" | 5.953 mm |
| 1/4" | 0.2500" | 6.350 mm |
| 17/64" | 0.2656" | 6.747 mm |
| 9/32" | 0.2813" | 7.144 mm |
| 5/16" | 0.3125" | 7.938 mm |
| 11/32" | 0.3438" | 8.731 mm |
| 3/8" | 0.3750" | 9.525 mm |
| 13/32" | 0.4063" | 10.319 mm |
| 7/16" | 0.4375" | 11.113 mm |
| 15/32" | 0.4688" | 11.906 mm |
| 1/2" | 0.5000" | 12.700 mm |
| 9/16" | 0.5625" | 14.288 mm |
| 5/8" | 0.6250" | 15.875 mm |
| 3/4" | 0.7500" | 19.050 mm |
| 1" | 1.0000" | 25.400 mm |
Source: ANSI drill bit size standards
Drill Bit Size Chart — Number Sizes (Wire Gauge)
| Number Size | Decimal Inches | Millimetres |
|---|---|---|
| #1 | 0.2280" | 5.791 mm |
| #2 | 0.2210" | 5.613 mm |
| #4 | 0.2090" | 5.309 mm |
| #6 | 0.2040" | 5.182 mm |
| #7 | 0.2010" | 5.105 mm |
| #10 | 0.1935" | 4.915 mm |
| #12 | 0.1890" | 4.801 mm |
| #16 | 0.1770" | 4.496 mm |
| #20 | 0.1610" | 4.089 mm |
| #25 | 0.1495" | 3.797 mm |
| #29 | 0.1360" | 3.454 mm |
| #30 | 0.1285" | 3.264 mm |
| #36 | 0.1065" | 2.705 mm |
| #40 | 0.0980" | 2.489 mm |
| #43 | 0.0890" | 2.261 mm |
| #44 | 0.0860" | 2.184 mm |
| #50 | 0.0700" | 1.778 mm |
| #55 | 0.0520" | 1.321 mm |
| #60 | 0.0400" | 1.016 mm |
| #80 | 0.0135" | 0.343 mm |
Source: ANSI/ASME B94.11M drill bit standard
Drill Bit Size Chart — Letter Sizes
| Letter Size | Decimal Inches | Millimetres |
|---|---|---|
| A | 0.2340" | 5.944 mm |
| B | 0.2380" | 6.045 mm |
| C | 0.2420" | 6.147 mm |
| D | 0.2460" | 6.248 mm |
| E | 0.2500" | 6.350 mm |
| F | 0.2570" | 6.528 mm |
| G | 0.2610" | 6.629 mm |
| H | 0.2660" | 6.756 mm |
| I | 0.2720" | 6.909 mm |
| J | 0.2770" | 7.036 mm |
| K | 0.2810" | 7.137 mm |
| L | 0.2900" | 7.366 mm |
| M | 0.2950" | 7.493 mm |
| N | 0.3020" | 7.671 mm |
| O | 0.3160" | 8.026 mm |
| P | 0.3230" | 8.204 mm |
| Q | 0.3320" | 8.433 mm |
| R | 0.3390" | 8.611 mm |
| S | 0.3480" | 8.839 mm |
| T | 0.3580" | 9.093 mm |
| U | 0.3680" | 9.347 mm |
| V | 0.3770" | 9.576 mm |
| W | 0.3860" | 9.804 mm |
| X | 0.3970" | 10.084 mm |
| Y | 0.4040" | 10.262 mm |
| Z | 0.4130" | 10.490 mm |
Source: ANSI letter drill bit size standard
Pilot Hole Size Guide for Screws
Drilling the correct pilot hole size before driving a screw prevents splitting wood, reduces driving torque, and produces a cleaner result.
| Screw Size | Pilot Hole for Softwood (pine, cedar) | Pilot Hole for Hardwood (oak, maple) | Clearance Hole (top piece) |
|---|---|---|---|
| #4 screw | 3/64" | 1/16" | 7/64" |
| #6 screw | 1/16" | 5/64" | 9/64" |
| #8 screw | 5/64" | 3/32" | 11/64" |
| #10 screw | 3/32" | 7/64" | 3/16" |
| #12 screw | 7/64" | 1/8" | 7/32" |
| #14 screw | 1/8" | 9/64" | 1/4" |
| 1/4" bolt | 13/64" | 13/64" | 17/64" |
| 5/16" bolt | 17/64" | 17/64" | 21/64" |
Source: Woodworking industry pilot hole guidelines
Drill Bit Size Finder
Enter a screw size or tap size to get the recommended drill bit for clearance and pilot holes. Toggle between metric and imperial. Includes material hardness guidance.
Frequently Asked Questions
What drill bit size do I need for a 1/4-inch bolt?
For a clearance hole through the top piece of a joint use a 17/64" drill bit. For a tapped hole in metal for a 1/4-20 screw use a #7 drill bit (0.201").
What is the difference between number, letter, and fractional drill bits?
Fractional drill bits are sized in fractions of an inch (1/16", 1/8" etc.) and are the most common for general use. Number and letter drill bits fill in the gaps between fractional sizes and are used in precision machining and for specific screw tap sizes.
What size drill bit do I need for a #8 wood screw?
For a #8 wood screw use a 5/64" pilot hole in softwood or 3/32" in hardwood. For a clearance hole through the top piece of a two-piece joint use 11/64".
What drill bit do I use for 1/2-inch diameter hole?
Use a 1/2" drill bit (0.500" — 12.700 mm). For precision work confirm the actual hole tolerance needed as drill bits produce holes slightly larger than their nominal size.
How do I convert drill bit sizes from inches to mm?
Multiply the decimal inch value by 25.4 to convert to millimetres. For example 3/8" equals 0.375" × 25.4 = 9.525 mm.
What is the most common drill bit size for home use?
1/8", 3/16", 1/4", and 3/8" are the most common sizes for general home use covering most pilot holes, wall anchors, and general drilling tasks. A 13-piece set covering 1/16" through 1/4" handles the vast majority of DIY applications.
What is a spade bit vs a twist drill bit?
A twist drill bit has a helical flute design and is used for general drilling in wood, metal, and plastic. A spade bit has a flat paddle shape and is designed specifically for fast boring of larger holes in wood only.
Can I use a metal drill bit on wood?
Yes — high-speed steel (HSS) drill bits designed for metal work on wood as well. However wood-specific bits such as brad point bits produce cleaner holes in wood with less tear-out.