Shop reference tools
Tap Size Chart
Map tap sizes to thread families, tap drill sizes, and calculator pages.
Tap 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. |
| M3 x 0.5 | 2.5 mm | 0.0984 | 2.50 | Approximate metric tap drill: major diameter minus pitch. |
| M4 x 0.7 | 3.3 mm | 0.1299 | 3.30 | Use published chart for production work. |
| M5 x 0.8 | 4.2 mm | 0.1654 | 4.20 | Common metric coarse thread. |
| M6 x 1 | 5.0 mm | 0.1969 | 5.00 | Common metric coarse thread. |
| M8 x 1.25 | 6.8 mm | 0.2677 | 6.80 | Common metric coarse thread. |
| M10 x 1.5 | 8.5 mm | 0.3346 | 8.50 | Common metric coarse thread. |
| M12 x 1.75 | 10.2 mm | 0.4016 | 10.20 | Common metric coarse thread. |