Drill Bit Size Chart | Complete Guide & Conversion Tables
Drill Bit Size Converter
Fractional to Decimal Conversion Chart
| Fraction (inches) | Decimal (inches) | Millimeters | Common Applications |
|---|---|---|---|
| 1/64" | 0.0156" | 0.397 mm | Precision electronics |
| 1/32" | 0.0313" | 0.794 mm | Small pilot holes |
| 3/64" | 0.0469" | 1.191 mm | Wire gauge holes |
| 1/16" | 0.0625" | 1.588 mm | Small wood screws |
| 5/64" | 0.0781" | 1.984 mm | Sheet metal work |
| 3/32" | 0.0938" | 2.381 mm | Pilot holes for #2 screws |
| 7/64" | 0.1094" | 2.778 mm | Pilot holes for #4 screws |
| 1/8" | 0.1250" | 3.175 mm | General purpose |
| 9/64" | 0.1406" | 3.572 mm | Pilot holes for #6 screws |
| 5/32" | 0.1563" | 3.969 mm | Pilot holes for #8 screws |
| 11/64" | 0.1719" | 4.366 mm | Pilot holes for #10 screws |
| 3/16" | 0.1875" | 4.763 mm | General woodworking |
| 13/64" | 0.2031" | 5.159 mm | Metalworking |
| 7/32" | 0.2188" | 5.556 mm | Pilot holes for 1/4" screws |
| 15/64" | 0.2344" | 5.953 mm | General purpose |
| 1/4" | 0.2500" | 6.350 mm | Common fastener size |
| 17/64" | 0.2656" | 6.747 mm | Clearance for 1/4" bolts |
| 9/32" | 0.2813" | 7.144 mm | Metalworking |
| 19/64" | 0.2969" | 7.541 mm | General purpose |
| 5/16" | 0.3125" | 7.938 mm | Common fastener size |
Letter Size Drill Bits (A-Z)
| Letter Size | Decimal (inches) | Millimeters | Common Uses |
|---|---|---|---|
| A | 0.234" | 5.944 | 1/4-28 tap drill |
| B | 0.238" | 6.045 | General purpose |
| C | 0.242" | 6.147 | 1/4-20 tap drill |
| D | 0.246" | 6.248 | General purpose |
| E | 0.250" | 6.350 | Clearance for #1 cap screw |
| F | 0.257" | 6.528 | General purpose |
| G | 0.261" | 6.629 | 5/16-24 tap drill |
| H | 0.266" | 6.756 | General purpose |
| I | 0.272" | 6.909 | 5/16-18 tap drill |
| J | 0.277" | 7.036 | General purpose |
| K | 0.281" | 7.137 | Clearance for #3 cap screw |
| L | 0.290" | 7.366 | General purpose |
| M | 0.295" | 7.493 | 3/8-24 tap drill |
| N | 0.302" | 7.671 | General purpose |
| O | 0.316" | 8.026 | 3/8-16 tap drill |
| P | 0.323" | 8.204 | General purpose |
| Q | 0.332" | 8.433 | 7/16-20 tap drill |
| R | 0.339" | 8.611 | General purpose |
| S | 0.348" | 8.839 | 7/16-14 tap drill |
| T | 0.358" | 9.093 | General purpose |
| U | 0.368" | 9.347 | 1/2-20 tap drill |
| V | 0.377" | 9.576 | General purpose |
| W | 0.386" | 9.804 | 1/2-13 tap drill |
| X | 0.397" | 10.084 | General purpose |
| Y | 0.404" | 10.262 | Clearance for 3/8" bolt |
| Z | 0.413" | 10.490 | General purpose |
Number Size Drill Bits (#1-80)
| Number Size | Decimal (inches) | Millimeters | Common Uses |
|---|---|---|---|
| #1 | 0.228" | 5.791 | 12-24 tap drill |
| #2 | 0.221" | 5.613 | General purpose |
| #3 | 0.213" | 5.410 | 10-32 tap drill |
| #4 | 0.209" | 5.309 | General purpose |
| #5 | 0.205" | 5.207 | 10-24 tap drill |
| #6 | 0.204" | 5.182 | General purpose |
| #7 | 0.201" | 5.105 | 1/4-20 tap drill |
| #8 | 0.199" | 5.055 | General purpose |
| #9 | 0.196" | 4.978 | 12-24 tap drill |
| #10 | 0.193" | 4.902 | General purpose |
Tap Drill Size Chart
| Screw Size | Threads per Inch | Tap Drill Size | Decimal Size | Millimeters |
|---|---|---|---|---|
| #4 | 40 | #43 | 0.089" | 2.26 |
| #6 | 32 | #36 | 0.1065" | 2.71 |
| #8 | 32 | #29 | 0.136" | 3.45 |
| #10 | 24 | #25 | 0.149" | 3.78 |
| #10 | 32 | #21 | 0.159" | 4.04 |
| 1/4" | 20 | #7 | 0.201" | 5.11 |
| 1/4" | 28 | #3 | 0.213" | 5.41 |
| 5/16" | 18 | F | 0.257" | 6.53 |
| 5/16" | 24 | I | 0.272" | 6.91 |
| 3/8" | 16 | 5/16" | 0.3125" | 7.94 |
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