🔧 Thread Sizes Reference
Bolt and screw thread specifications for Unified National Coarse (UNC) and Metric (ISO) thread standards. Each entry includes major diameter, thread pitch, and recommended tap drill size.
Unified National Coarse (UNC) Threads
| Size | Major Diam. (in) | TPI | Tap Drill |
|---|---|---|---|
| #0-80 | 0.0600 | 80 | #56 (0.0465") |
| #1-64 | 0.0730 | 64 | #53 (0.0595") |
| #2-56 | 0.0860 | 56 | #50 (0.0700") |
| #3-48 | 0.0990 | 48 | #47 (0.0785") |
| #4-40 | 0.1120 | 40 | #43 (0.0890") |
| #6-32 | 0.1380 | 32 | #36 (0.1065") |
| #8-32 | 0.1640 | 32 | #29 (0.1360") |
| #10-24 | 0.1900 | 24 | #25 (0.1495") |
| #12-24 | 0.2160 | 24 | #16 (0.1770") |
| 1/4-20 | 0.2500 | 20 | #7 (0.2010") |
| 5/16-18 | 0.3125 | 18 | F (0.2570") |
| 3/8-16 | 0.3750 | 16 | 5/16" (0.3125") |
| 7/16-14 | 0.4375 | 14 | U (0.3680") |
| 1/2-13 | 0.5000 | 13 | 27/64" (0.4219") |
| 9/16-12 | 0.5625 | 12 | 31/64" (0.4844") |
| 5/8-11 | 0.6250 | 11 | 17/32" (0.5313") |
| 3/4-10 | 0.7500 | 10 | 21/32" (0.6563") |
| 7/8-9 | 0.8750 | 9 | 49/64" (0.7656") |
| 1-8 | 1.0000 | 8 | 7/8" (0.8750") |
Metric (ISO) Threads — Coarse Pitch
| Size | Pitch (mm) | Major Diam. (mm) | Tap Drill |
|---|---|---|---|
| M1 | 0.25 | 1.0 | 0.75 mm |
| M1.2 | 0.25 | 1.2 | 0.95 mm |
| M1.6 | 0.35 | 1.6 | 1.25 mm |
| M2 | 0.40 | 2.0 | 1.60 mm |
| M2.5 | 0.45 | 2.5 | 2.05 mm |
| M3 | 0.50 | 3.0 | 2.50 mm |
| M4 | 0.70 | 4.0 | 3.30 mm |
| M5 | 0.80 | 5.0 | 4.20 mm |
| M6 | 1.00 | 6.0 | 5.00 mm |
| M8 | 1.25 | 8.0 | 6.75 mm |
| M10 | 1.50 | 10.0 | 8.50 mm |
| M12 | 1.75 | 12.0 | 10.25 mm |
| M14 | 2.00 | 14.0 | 12.00 mm |
| M16 | 2.00 | 16.0 | 14.00 mm |
| M18 | 2.50 | 18.0 | 15.50 mm |
| M20 | 2.50 | 20.0 | 17.50 mm |
| M24 | 3.00 | 24.0 | 21.00 mm |
| M30 | 3.50 | 30.0 | 26.50 mm |