Metric Tap and Drill Chart (MM Sizes)
This metric tap drill chart provides recommended drill sizes for metric threads in millimeters (mm), helping ensure proper thread engagement, accuracy, and consistent results in machining and fabrication applications.
Use the chart below to find the correct drill size for common metric thread sizes.
| Drill Bit Size Category | Drill Bit Size | Decimal Inch Size | Metric mm Size | Tap or Screw Size | Tap Or Screw Size Category | Thread Standard |
|---|---|---|---|---|---|---|
| Metric | 1.25mm | 0.0492 | 1.25 | M1.6x0.35 | Metric | Coarse |
| Metric | 1.45mm | 0.0571 | 1.45 | M1.8x0.35 | Metric | Coarse |
| Metric | 1.6mm | 0.0630 | 1.60 | M2x0.4 | Metric | Coarse |
| Metric | 1.75mm | 0.0689 | 1.75 | M2.2x0.45 | Metric | Coarse |
| Metric | 1.9mm | 0.0748 | 1.90 | M2.3x0.4 | Metric | Coarse |
| Metric | 2.05mm | 0.0807 | 2.05 | M2.5x0.45 | Metric | Coarse |
| Metric | 2.15mm | 0.0846 | 2.15 | M2.6x0.45 | Metric | Coarse |
| Metric | 2.5mm | 0.0984 | 2.50 | M3x0.5 | Metric | Coarse |
| Metric |
2.9mm |
0.1142 | 2.90 | M3.5x0.6 | Metric | Coarse |
| Metric | 3.3mm | 0.1299 | 3.30 | M4x0.7 | Metric | Coarse |
| Metric | 3.75mm | 0.1476 | 3.75 | M4.5x0.75 | Metric | Coarse |
| Metric | 4.2mm | 0.1654 |
4.20 |
M5x0.8 | Metric | Coarse |
| Metric | 5mm | 0.1969 | 5.00 | M6x1 | Metric | Coarse |
| Metric | 5.25mm | 0.2067 | 5.25 | M6x0.75 | Metric | Fine |
| Metric | 6mm | 0.2362 | 6.00 | M7x1 | Metric | Coarse |
| Metric | 17/64 | 0.2657 | 6.75 | M8x1.25 | Metric | Coarse |
| Metric | 7mm |
0.2756 | 7.00 | M8x1 | Metric | Fine |
| Metric | 7.75mm | 0.3051 | 7.75 | M9x1.25 | Metric | Coarse |
| Metric | 8.5mm |
0.3346 | 8.50 | M10x1.5 | Metric | Coarse |
| Metric | 8.75mm |
0.3445 | 8.75 | M10x1.25 | Metric | Fine |
| Metric | 9mm | 0.3543 | 9.00 | M10x1 | Metric | Extra Fine |
| Metric | 9.5mm | 0.3740 | 9.50 | M11x1.5 | Metric | Coarse |
| Letter | Y |
0.4040 | 10.26 | M12x1.75 | Metric | Coarse |
| Inch | 27/64 | 0.4219 | 10.72 | M12x1.25 | Metric | Fine |
| Metric | 12mm | 0.4724 | 12.00 | M14x2 | Metric | Coarse |
| Metric | 12.5mm | 0.4921 | 12.50 | M14x1.5 | Metric | Fine |
| Inch | 1/2 |
0.5000 | 12.70 | M14x1.25 | Metric | Extra Fine |
| Metric | 14mm |
0.5512 | 14.00 | M16x2 | Metric | Coarse |
| Metric | 14.5mm | 0.5709 | 14.50 | M16x1.5 | Metric | Fine |
| Metric | 15.5mm | 0.6102 | 15.50 | M18x2.5 | Metric | Coarse |
| Metric | 16mm | 0.6299 | 16.00 |
M18x2 | Metric | Extra Fine |
| Metric | 17.5mm |
0.6890 | 17.50 | M20x2.5 | Metric | Coarse |
| Metric | 18mm | 0.7087 | 18.00 | M20x2 | Metric | Fine |
| Metric | 18.5mm |
0.7283 | 18.50 | M20x1.5 | Metric | Extra Fine |
| Metric | 19.5mm |
0.7677 | 19.50 | M22x2.5 | Metric | Coarse |
| Metric | 20mm | 0.7874 | 20.00 | M22x2 | Metric | Fine |
| Metric | 20.5mm | 0.8071 | 20.50 | M22x1.5 | Metric | Extra Fine |
| Metric | 21mm |
0.8268 | 21.00 | M24x3 | Metric | Coarse |
| Metric | 22mm |
0.8661 | 22.00 | M24x2 | Metric | Fine |
| Metric |
22.5mm |
0.8858 | 22.50 | M24x1.5 | Metric | Extra Fine |
| Metric | 24mm | 0.9449 | 24.00 | M27x3 | Metric | Coarse |
| Metric | 25mm | 0.9843 | 25.00 | M27x2 | Metric | Fine |
| Metric | 26.5mm | 1.0433 | 26.50 | M30x3.5 | Metric | Coarse |
| Metric | 28mm |
1.1024 |
28.00 | M30x2 | Metric | Fine |
Understanding Metric Tap Drill Sizes
Metric tap drill sizes are used to determine the correct hole diameter before tapping metric threads. These sizes are typically expressed in millimeters (mm) and are based on the thread’s major diameter and pitch. A common method to estimate metric tap drill sizes is to subtract the thread pitch from the major diameter.
Selecting the proper drill size ensures the correct balance between thread engagement and tapping efficiency. Using the wrong size can lead to poor thread quality, excessive tool wear, or tap failure.
How to Use a Metric Tap Drill Chart
- Identify the thread size (for example, M6 x 1.0 or M10 x 1.5).
- Locate the corresponding drill size in millimeters.
- Drill the hole to the recommended size before tapping.
- Apply proper cutting fluid and tapping technique for best results.
Why Drill Size Matters for Metric Threads
Proper drill sizing is essential to achieve the correct percentage of thread engagement. A hole that is too small increases tapping torque and tool wear, while a hole that is too large reduces thread strength and holding capability.
In many applications, a standard tap drill size provides approximately 70–75% thread engagement, which is suitable for most general machining operations.
Metric Thread Sizes and Pitch
Metric threads are defined by their major diameter and pitch. For example, an M8 x 1.25 thread has a nominal diameter of 8 mm and a thread pitch of 1.25 mm. The pitch directly affects the recommended tap drill size. For example, an M10 x 1.5 thread typically uses an 8.5 mm drill size.
This chart includes common metric sizes used in manufacturing, maintenance, and engineering applications.
Printable Metric Tap Drill Chart
Download a printable PDF version of this metric tap drill chart for convenient reference in the shop or on the job site.
Related Tap Drill Charts
Frequently Asked Questions
What is a metric tap drill chart?
A metric tap drill chart shows the recommended drill sizes in millimeters for tapping metric threads. It helps match thread size and pitch to the correct hole diameter.
How do I find the drill size for a metric tap?
Identify the thread size and pitch (for example, M8 x 1.25), then use a metric tap drill chart to find the recommended drill size in millimeters before tapping.
Why are metric tap drill sizes given in millimeters?
Metric threads are standardized using millimeters for both diameter and pitch, so tap drill sizes are also provided in millimeters to maintain consistency and accuracy.
What percentage of thread engagement do metric tap drill sizes provide?
Most standard metric tap drill sizes provide approximately 70–75% thread engagement, which balances strength and ease of tapping for most applications.
Is there a printable version of this metric tap drill chart?
Yes. A printable PDF version is available for convenient use in machining, maintenance, and fabrication environments.
