Thread size chart
Basic major, pitch and minor diameters for Unified (UNC, UNF) and ISO metric threads, with threads per inch converted to pitch.
| Thread | TPI | Pitch (mm) | Major Ø | Pitch Ø | Minor Ø |
|---|---|---|---|---|---|
| #1-64 | 64 | 0.3969 | 0.0730 | 0.0629 | 0.0538 |
| #2-56 | 56 | 0.4536 | 0.0860 | 0.0744 | 0.0641 |
| #3-48 | 48 | 0.5292 | 0.0990 | 0.0855 | 0.0734 |
| #4-40 | 40 | 0.635 | 0.1120 | 0.0958 | 0.0813 |
| #5-40 | 40 | 0.635 | 0.1250 | 0.1088 | 0.0943 |
| #6-32 | 32 | 0.7938 | 0.1380 | 0.1177 | 0.0997 |
| #8-32 | 32 | 0.7938 | 0.1640 | 0.1437 | 0.1257 |
| #10-24 | 24 | 1.0583 | 0.1900 | 0.1629 | 0.1389 |
| #10-32 | 32 | 0.7938 | 0.1900 | 0.1697 | 0.1517 |
| 1/4-20 | 20 | 1.27 | 0.2500 | 0.2175 | 0.1887 |
| 5/16-18 | 18 | 1.4111 | 0.3125 | 0.2764 | 0.2443 |
| 3/8-16 | 16 | 1.5875 | 0.3750 | 0.3344 | 0.2983 |
| 7/16-14 | 14 | 1.8143 | 0.4375 | 0.3911 | 0.3499 |
| 1/2-13 | 13 | 1.9538 | 0.5000 | 0.4500 | 0.4056 |
| 5/8-11 | 11 | 2.3091 | 0.6250 | 0.5660 | 0.5135 |
| 3/4-10 | 10 | 2.54 | 0.7500 | 0.6850 | 0.6273 |
| 7/8-9 | 9 | 2.8222 | 0.8750 | 0.8028 | 0.7387 |
| 1"-8 | 8 | 3.175 | 1.0000 | 0.9188 | 0.8466 |
| Thread | TPI | Pitch (mm) | Major Ø | Pitch Ø | Minor Ø |
|---|---|---|---|---|---|
| #0-80 | 80 | 0.3175 | 0.0600 | 0.0519 | 0.0447 |
| #1-72 | 72 | 0.3528 | 0.0730 | 0.0640 | 0.0560 |
| #2-64 | 64 | 0.3969 | 0.0860 | 0.0759 | 0.0668 |
| #4-48 | 48 | 0.5292 | 0.1120 | 0.0985 | 0.0864 |
| #6-40 | 40 | 0.635 | 0.1380 | 0.1218 | 0.1073 |
| #8-36 | 36 | 0.7056 | 0.1640 | 0.1460 | 0.1299 |
| #10-32 | 32 | 0.7938 | 0.1900 | 0.1697 | 0.1517 |
| 1/4-28 | 28 | 0.9071 | 0.2500 | 0.2268 | 0.2062 |
| 5/16-24 | 24 | 1.0583 | 0.3125 | 0.2854 | 0.2614 |
| 3/8-24 | 24 | 1.0583 | 0.3750 | 0.3479 | 0.3239 |
| 7/16-20 | 20 | 1.27 | 0.4375 | 0.4050 | 0.3762 |
| 1/2-20 | 20 | 1.27 | 0.5000 | 0.4675 | 0.4387 |
| 9/16-18 | 18 | 1.4111 | 0.5625 | 0.5264 | 0.4943 |
| 3/4-16 | 16 | 1.5875 | 0.7500 | 0.7094 | 0.6733 |
| Thread | Pitch (mm) | Major Ø | Pitch Ø | Minor Ø |
|---|---|---|---|---|
| M3×0.5 | 0.5 | 3.000 | 2.675 | 2.459 |
| M4×0.7 | 0.7 | 4.000 | 3.545 | 3.242 |
| M5×0.8 | 0.8 | 5.000 | 4.480 | 4.134 |
| M6×1.0 | 1 | 6.000 | 5.350 | 4.917 |
| M8×1.25 | 1.25 | 8.000 | 7.188 | 6.647 |
| M10×1.5 | 1.5 | 10.000 | 9.026 | 8.376 |
| M12×1.75 | 1.75 | 12.000 | 10.863 | 10.106 |
| M14×2.0 | 2 | 14.000 | 12.701 | 11.835 |
| M16×2.0 | 2 | 16.000 | 14.701 | 13.835 |
| M20×2.5 | 2.5 | 20.000 | 18.376 | 17.294 |
| M24×3.0 | 3 | 24.000 | 22.051 | 20.752 |
Common questions
- How do I convert threads per inch to pitch?
- Pitch in millimeters = 25.4 ÷ TPI. A 20 TPI thread has a 1.27 mm pitch.
- What is the difference between UNC and UNF?
- UNF has more threads per inch at the same diameter: finer adjustment and more strength in thin walls, but slower to assemble and easier to cross-thread.