Drill Bit Size Chart
Standard drill bit sizes range from 1/16 inch to 1/2 inch in fractional increments. The chart below lists every common fractional drill bit size with its decimal inch equivalent, metric conversion in millimeters, wire gauge number, and typical applications. Use this reference to find the right drill bit for pilot holes, tap drilling, and general-purpose boring.
| Fractional | Decimal (in) | Metric (mm) | Wire Gauge | Common Use |
|---|---|---|---|---|
| 1/16" | 0.0625" | 1.59 mm | #52 | Pilot holes for #2 screws |
| 5/64" | 0.0781" | 1.98 mm | #46 | Pilot holes for #3 screws |
| 3/32" | 0.0938" | 2.38 mm | #42 | Pilot holes for #4 screws in hardwood |
| 7/64" | 0.1094" | 2.78 mm | #36 | Pilot holes for #6 screws in hardwood |
| 1/8" | 0.1250" | 3.18 mm | #30 | General purpose, pilot holes for #6-#8 screws |
| 9/64" | 0.1406" | 3.57 mm | #28 | Pilot holes for #8 screws in hardwood |
| 5/32" | 0.1563" | 3.97 mm | #22 | Pilot holes for #8-#10 screws |
| 11/64" | 0.1719" | 4.37 mm | #18 | Pilot holes for #10 screws in hardwood |
| 3/16" | 0.1875" | 4.76 mm | #13 | General purpose, wall anchors |
| 13/64" | 0.2031" | 5.16 mm | #7 | Pilot holes for #12 screws |
| 7/32" | 0.2188" | 5.56 mm | #2 | Pilot holes for #14 screws |
| 15/64" | 0.2344" | 5.95 mm | A | Tap drill for #12-24 threads |
| 1/4" | 0.2500" | 6.35 mm | F | Most common size, wall anchors, general drilling |
| 9/32" | 0.2813" | 7.14 mm | L | Tap drill for 5/16-18 threads |
| 5/16" | 0.3125" | 7.94 mm | O | Medium fasteners, lag bolt pilot holes |
| 11/32" | 0.3438" | 8.73 mm | R | Tap drill for 3/8-16 threads |
| 3/8" | 0.3750" | 9.53 mm | V | Lag bolt pilot holes, general construction |
| 13/32" | 0.4063" | 10.32 mm | X | Tap drill for 7/16-14 threads |
| 7/16" | 0.4375" | 11.11 mm | — | Large fastener pilot holes |
| 15/32" | 0.4688" | 11.91 mm | — | Tap drill for 1/2-13 threads |
| 1/2" | 0.5000" | 12.70 mm | — | Large holes, conduit, plumbing |
How to Read This Chart
Fractional vs Decimal
Fractional sizes like 1/4" are the most common way drill bits are sold. The decimal equivalent is useful when comparing to metric sizes or using precision measuring tools like calipers.
Pilot Hole Sizing
For wood screws, choose a drill bit slightly smaller than the screw shank diameter. In hardwood, the pilot hole should be closer to the screw size. In softwood, you can use a smaller pilot hole or skip it for small screws.
Wire Gauge Numbers
Wire gauge (number and letter) drill bits fill the gaps between fractional sizes. Lower numbers are larger. Letter sizes A through Z continue above number sizes, with A being the smallest letter size.
Material Considerations
Use HSS (high-speed steel) bits for wood and soft metals. Choose cobalt or carbide bits for stainless steel and hardened materials. Masonry bits with carbide tips are required for concrete, brick, and stone.
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