Thread size table
Nominal diameter, pitch and tap drill size by thread standard.
Metric
| Size | Ø nominal | Pitch / TPI | Tap drill |
|---|---|---|---|
| M3 | 3 mm | 0.5 mm | 2.5 mm |
| M4 | 4 mm | 0.7 mm | 3.3 mm |
| M5 | 5 mm | 0.8 mm | 4.2 mm |
| M6 | 6 mm | 1 mm | 5 mm |
| M8 | 8 mm | 1.25 mm | 6.8 mm |
| M10 | 10 mm | 1.5 mm | 8.5 mm |
| M12 | 12 mm | 1.75 mm | 10.2 mm |
| M14 | 14 mm | 2 mm | 12 mm |
| M16 | 16 mm | 2 mm | 14 mm |
| M18 | 18 mm | 2.5 mm | 15.5 mm |
| M20 | 20 mm | 2.5 mm | 17.5 mm |
| M22 | 22 mm | 2.5 mm | 19.5 mm |
| M24 | 24 mm | 3 mm | 21 mm |
UNC
| Size | Ø nominal | Pitch / TPI | Tap drill |
|---|---|---|---|
| 1/4-20 | 0.25" | 20 TPI | 0.201" |
| 5/16-18 | 0.3125" | 18 TPI | 0.257" |
| 3/8-16 | 0.375" | 16 TPI | 0.3125" |
| 7/16-14 | 0.4375" | 14 TPI | 0.368" |
| 1/2-13 | 0.5" | 13 TPI | 0.4219" |
| 9/16-12 | 0.5625" | 12 TPI | 0.4844" |
| 5/8-11 | 0.625" | 11 TPI | 0.5312" |
| 3/4-10 | 0.75" | 10 TPI | 0.6562" |
| 7/8-9 | 0.875" | 9 TPI | 0.7656" |
| 1-8 | 1" | 8 TPI | 0.875" |
UNF
| Size | Ø nominal | Pitch / TPI | Tap drill |
|---|---|---|---|
| 1/4-28 | 0.25" | 28 TPI | 0.213" |
| 5/16-24 | 0.3125" | 24 TPI | 0.272" |
| 3/8-24 | 0.375" | 24 TPI | 0.332" |
| 7/16-20 | 0.4375" | 20 TPI | 0.3906" |
| 1/2-20 | 0.5" | 20 TPI | 0.4531" |
| 9/16-18 | 0.5625" | 18 TPI | 0.5156" |
| 5/8-18 | 0.625" | 18 TPI | 0.5781" |
| 3/4-16 | 0.75" | 16 TPI | 0.6875" |
| 7/8-14 | 0.875" | 14 TPI | 0.8125" |
| 1-12 | 1" | 12 TPI | 0.9219" |
Reference values only - always verify against the actual part before machining, tapping or tightening anything.