AmesWeb
Metric Tap Drill Chart & Calculator
ISO metric threads • Coarse & Fine • Sizes in mm
Use the instant calculator to get the recommended tap drill size for ISO metric threads, or scroll the chart for a quick lookup.
Instant Metric Tap Drill Calculator
Quick rule of thumb: tap drill ≈ major diameter − pitch (varies by standard, % thread and application).
Metric Tap Drill Chart
Scroll the chart for a quick lookup. Dimensions are in millimetres.
|
Metric Tap Drill Chart - Coarse Thread |
|
Coarse Pitch Thread |
Drill size (mm) |
|
Tap Size |
Basic Major
Dia. |
Thread Pitch |
Minor diameter for class |
|
5H
max. |
6H max. |
7H max. |
5H, 6H, 7H min |
|
M1.6 x 0.35 |
1.6 |
0.35 |
1.301 |
1.321 |
- |
1.221 |
1.25 |
|
M2 x 0.4 |
2 |
0.4 |
1.657 |
1.679 |
- |
1.567 |
1.60 |
|
M2.5 x 0.45 |
2.5 |
0.45 |
2.113 |
2.138 |
- |
2.013 |
2.05 |
|
M3 x 0.5 |
3 |
0.5 |
2.571 |
2.599 |
2.639 |
2.459 |
2.50 |
|
M3.5* x 0.6 |
3.5 |
0.6 |
2.975 |
3.010 |
3.050 |
2.850 |
2.90 |
|
M4 x 0.7 |
4 |
0.7 |
3.382 |
3.422 |
3.466 |
3.242 |
3.30 |
|
M5 x 0.8 |
5 |
0.8 |
4.294 |
4.334 |
4.384 |
4.134 |
4.20 |
|
M6 x 1 |
6 |
1 |
5.107 |
5.153 |
5.217 |
4.917 |
5.00 |
|
M8 x 1.25 |
8 |
1.25 |
6.859 |
6.912 |
6.982 |
6.647 |
6.80 |
|
M10 x 1.5 |
10 |
1.5 |
8.612 |
8.676 |
8.751 |
8.376 |
8.50 |
|
Coarse Pitch Thread |
Drill size (mm) |
|
Tap Size |
Basic Major
Dia. |
Thread Pitch |
Minor diameter for class |
|
5H
max. |
6H max. |
7H max. |
5H, 6H, 7H min |
|
M12 x 1.75 |
12 |
1.75 |
10.371 |
10.441 |
10.531 |
10.106 |
10.20 |
|
M14* x 2 |
14 |
2 |
12.135 |
12.210 |
12.310 |
11.835 |
12.00 |
|
M16 x 2 |
16 |
2 |
14.135 |
14.210 |
14.310 |
13.835 |
14.00 |
|
M18* x 2.5 |
18 |
2.5 |
15.649 |
15.744 |
15.854 |
15.294 |
15.50 |
|
M20 x 2.5 |
20 |
2.5 |
17.649 |
17.744 |
17.854 |
17.294 |
17.50 |
|
M22* x 2.5 |
22 |
2.5 |
19.649 |
19.744 |
19.854 |
19.294 |
19.50 |
|
M24 x 3 |
24 |
3 |
21.152 |
21.252 |
21.382 |
20.752 |
21.00 |
|
M27* x 3 |
27 |
3 |
24.152 |
24.252 |
24.382 |
23.752 |
24.00 |
|
M30 x 3.5 |
30 |
3.5 |
26.661 |
26.771 |
26.921 |
26.211 |
26.50 |
|
Coarse Pitch Thread |
Drill size (mm) |
|
Tap Size |
Basic Major
Dia. |
Thread Pitch |
Minor diameter for class |
|
5H
max. |
6H max. |
7H max. |
5H, 6H, 7H min |
|
M33* x 3.5 |
33 |
3.5 |
29.661 |
29.771 |
29.921 |
29.211 |
29.50 |
|
M36 x 4 |
36 |
4 |
32.145 |
32.270 |
32.420 |
31.670 |
32.00 |
|
M39* x 4 |
39 |
4 |
35.145 |
35.270 |
35.420 |
34.670 |
35.00 |
|
M42 x 4.5 |
42 |
4.5 |
37.659 |
37.799 |
37.979 |
37.129 |
37.50 |
|
M45* x 4.5 |
45 |
4.5 |
40.659 |
40.799 |
40.979 |
40.129 |
40.50 |
|
M48 x 5 |
48 |
5 |
43.147 |
43.297 |
43.487 |
42.587 |
43.00 |
|
M52* x 5 |
52 |
5 |
47.147 |
47.297 |
47.487 |
46.587 |
47.00 |
|
M56 x 5.5 |
56 |
5.5 |
50.646 |
50.796 |
50.996 |
50.046 |
50.50 |
Note : * Non-preferred threads according to standard.
|
Metric Tap Drill Chart - Fine Thread |
|
Fine Pitch Thread |
Drill size (mm) |
|
Tap Size |
Basic Major
Dia. |
Thread Pitch |
Minor diameter for class |
|
5H
max. |
6H max. |
7H max. |
5H, 6H, 7H min |
|
M8 x 1 |
8 |
1 |
7.107 |
7.153 |
7.217 |
6.917 |
7.00 |
|
M10 x 1 |
10 |
1 |
9.107 |
9.153 |
9.217 |
8.917 |
9.00 |
|
M10* x 1.25 |
10 |
1.25 |
8.859 |
8.912 |
8.982 |
8.647 |
8.80 |
|
M12* x 1.25 |
12 |
1.25 |
10.859 |
10.912 |
10.982 |
10.647 |
10.80 |
|
M12 x 1.5 |
12 |
1.5 |
10.612 |
10.676 |
10.751 |
10.376 |
10.50 |
|
M14* x 1.5 |
14 |
1.5 |
12.612 |
12.676 |
12.751 |
12.376 |
12.50 |
|
M16 x 1.5 |
16 |
1.5 |
14.612 |
14.676 |
14.751 |
14.376 |
14.50 |
|
M18* x 1.5 |
18 |
1.5 |
16.612 |
16.676 |
16.751 |
16.376 |
16.50 |
|
M20 x 1.5 |
20 |
1.5 |
18.612 |
18.676 |
18.751 |
18.376 |
18.50 |
|
M20* x 2 |
20 |
2 |
18.135 |
18.210 |
18.310 |
17.835 |
18.00 |
|
Coarse Pitch Thread |
Drill size (mm) |
|
Tap Size |
Basic Major
Dia. |
Thread Pitch |
Minor diameter for class |
|
5H
max. |
6H max. |
7H max. |
5H, 6H, 7H min |
|
M22* x 1.5 |
22 |
1.5 |
20.612 |
20.676 |
20.751 |
20.376 |
20.50 |
|
M24 x 2 |
24 |
2 |
22.135 |
22.210 |
22.310 |
21.835 |
22.00 |
|
M27* x 2 |
27 |
2 |
25.135 |
25.210 |
25.310 |
24.835 |
25.00 |
|
M30 x 2 |
30 |
2 |
28.135 |
28.210 |
28.310 |
27.835 |
28.00 |
|
M33* x 2 |
33 |
2 |
31.135 |
31.210 |
31.310 |
30.835 |
31.00 |
|
M36 x 3 |
36 |
3 |
33.152 |
33.252 |
33.382 |
32.752 |
33.00 |
|
M39* x 3 |
39 |
3 |
36.152 |
36.252 |
36.382 |
36.752 |
36.00 |
|
M42 x 3 |
42 |
3 |
39.152 |
39.252 |
39.382 |
38.752 |
39.00 |
|
M45* x 3 |
45 |
3 |
42.152 |
42.252 |
42.382 |
41.752 |
42.00 |
|
M48 x 3 |
48 |
3 |
45.152 |
45.252 |
45.382 |
44.752 |
45.00 |
|
M52* x 4 |
52 |
4 |
48.145 |
48.270 |
48.420 |
47.670 |
48.00 |
Note : * Non-preferred threads according to standard.
Supplements:
Reference:
-
ISO 68-1:1998(E) - ISO general purpose screw threads — Basic profile — Part 1: Metric screw threads
-
ISO 2306:1972, Drills for use prior to tapping screw threads
FAQ
What drill size do I use for an M6 x 1 tap?
Use the calculator above (select M6 x 1) or find it in the coarse-thread chart below. The recommended drill diameter is shown in mm.
Is this chart for coarse and fine metric threads?
Yes. The page includes tables for both coarse and fine ISO metric threads, plus a calculator for quick lookup.
How do I choose between two nearby drill sizes?
When you have a choice, selecting a slightly larger drill (within the standard limits) can reduce tapping torque and breakage risk, especially in tougher materials.