Shop reference tools
Drill and Tap Chart
Match common taps to drill sizes, decimal equivalents, and working notes.
Drill and Tap 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. |
What is a drill and tap chart?
A drill and tap chart pairs each tap thread with the drill size used before cutting threads. Use it when the job starts with a fastener callout such as #10-32, 1/4-28 UNF, or M8 x 1.25 and you need the starting hole.
How do I avoid mixing tap drill and clearance holes?
A tap drill hole is smaller because the tap cuts or forms threads. A clearance hole is larger because the screw or bolt passes through. If the part is not being tapped, use the clearance hole chart instead.
Should I use the chart or the tap drill calculator?
Use the chart for common shop sizes. Use the calculator when you need to understand how pitch, thread percentage, and metric estimates affect the result. For critical work, compare both with the drawing or tooling recommendation.
What thread percentage do these tap drill sizes assume?
Many general tap drill charts are built around a practical thread-engagement target rather than a universal rule. Higher thread percentage usually means a smaller drilled hole and more tapping load. Lower thread percentage usually means a larger hole and easier tapping, with less thread engagement.
Why do tap drill charts give different answers?
Different references can assume different tap types, materials, thread percentages, fit classes, or rounding to available drill sizes. Use this chart as a starting point, then check the drawing, tap maker, and material before cutting final parts.
When should I not use a general tap drill chart?
Do not rely on a general chart alone for forming taps, pipe threads, plated parts, blind holes, unusual materials, or any job with a specified thread class. Those cases need the supplier chart or engineering drawing to control the final drill size.
Common tap drill sizes worth checking first
Use these common rows as entry points, then confirm the full thread callout before opening the chart or calculator.