Shop reference tools
Metric Tap Drill Chart
Reference metric tap drill sizes for M3 through M12 coarse threads.
Metric Tap Drill 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 |
|---|---|---|---|---|
| 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 drill size is used for common metric taps?
For common metric coarse taps, quick reference values include M6 x 1 at 5.0 mm, M8 x 1.25 at 6.8 mm, M10 x 1.5 at 8.5 mm by the basic metric estimate shown on this site, and M12 x 1.75 at 10.2 mm by the same estimate.
What is the drill size for M8 x 1.25?
Use 6.8 mm as the common starting value for M8 x 1.25. If a chart or tap manufacturer lists a nearby alternate, compare the stated thread percentage and material assumptions before substituting.
How do I calculate metric tap drill size?
The quick metric estimate is major diameter minus pitch. That is why M6 x 1 starts near 5.0 mm and M8 x 1.25 starts near 6.75 mm, rounded to a practical drill. Published charts may choose a nearby value to target a specific thread percentage.
Metric tap drill chart vs calculator
Use the chart when the thread callout is common and the shop standard is already known. Use the tap drill calculator when you need to compare a different thread percentage or explain why two references disagree.