Metric Tap Drill Chart
Use this metric tap drill chart to quickly look up common drill sizes for metric threads from M3 through M20. This page is intended as a fast shop-floor and engineering reference for machining, fixture building, maintenance, and machine design.
This chart is most useful as a practical starting reference. Real drill selection can change depending on whether you want easier tapping, higher thread percentage, form tapping, tough materials, or production repeatability.
| Thread Size | Pitch (mm) | Tap Drill (mm) |
|---|---|---|
| M3 × 0.5 | 0.5 | 2.5 |
| M4 × 0.7 | 0.7 | 3.3 |
| M5 × 0.8 | 0.8 | 4.2 |
| M6 × 1.0 | 1.0 | 5.0 |
| M8 × 1.25 | 1.25 | 6.8 |
| M10 × 1.5 | 1.5 | 8.5 |
| M12 × 1.75 | 1.75 | 10.2 |
| M14 × 2.0 | 2.0 | 12.0 |
| M16 × 2.0 | 2.0 | 14.0 |
| M18 × 2.5 | 2.5 | 15.5 |
| M20 × 2.5 | 2.5 | 17.5 |
Metric Tap Drill Calculator
Select a thread size and pitch to estimate the recommended tap drill diameter using the common major diameter minus pitch method.
Need more fastening and machining references?
Use the related charts and calculators to move from drilled hole size into torque, clamp load, and fastening setup decisions.
Browse Reference ChartsWhat affects final tap drill choice?
Major diameter minus pitch is a great quick estimate, but final drill selection can change depending on material, desired thread percentage, tap style, and process stability. Harder materials or tougher tapping conditions may benefit from a slightly larger drill if reduced tap load matters more than maximum thread engagement.
Production work also depends on tool wear, hole quality, tolerance, cutting fluid, and whether the thread is cut or formed. So this page is best used as a practical starting point, not as the only decision for critical parts.