Shop reference tools
Thread Size Chart
Connect screw and bolt thread sizes to tap drill and pitch references.
Thread Size Chart lookup
Start with the table, then use the related pages for tapping, clearance holes, pilot holes, and printable shop sheets.
| Thread | Tap drill | Decimal inch | Millimeters | Working note |
|---|---|---|---|---|
| #4-40 UNC | #43 | 0.0890 | 2.26 | Common machine-screw tap size. |
| #6-32 UNC | #36 | 0.1065 | 2.71 | Useful for light machine screws. |
| #8-32 UNC | #29 | 0.1360 | 3.45 | Check thin material and thread depth. |
| #10-24 UNC | #25 | 0.1495 | 3.80 | Coarse #10 machine screw thread. |
| #10-32 UNF | #21 | 0.1590 | 4.04 | Fine #10 machine screw thread. |
| 1/4-20 UNC | #7 | 0.2010 | 5.11 | Common quarter-inch coarse tap. |
| 1/4-28 UNF | #3 | 0.2130 | 5.41 | Fine quarter-inch tap. |
| 5/16-18 UNC | F | 0.2570 | 6.53 | Coarse 5/16 inch tap. |
| 5/16-24 UNF | I | 0.2720 | 6.91 | Fine 5/16 inch tap. |
| 3/8-16 UNC | 5/16 | 0.3125 | 7.94 | Common coarse 3/8 inch tap. |
| 3/8-24 UNF | Q | 0.3320 | 8.43 | Fine 3/8 inch tap. |
| 1/2-13 UNC | 27/64 | 0.4219 | 10.72 | Coarse half-inch tap. |
| 1/2-20 UNF | 29/64 | 0.4531 | 11.51 | Fine half-inch tap. |