UNF Thread Chart (Unified Fine)
All 24 Unified fine threads from #0-80 to 1-1/2-12, with diameters, tap drill and tensile stress area. UNF is the fine-pitch alternative to UNC and the usual choice in automotive and aerospace fasteners.
| Thread | TPI | Major Ø (in) | Pitch Ø (in) | Minor Ø D1 (in) | Tap drill | Drill (in) | Drill (mm) | % thread | Stress area (in²) |
|---|---|---|---|---|---|---|---|---|---|
| #0-80 UNF | 80 | 0.0600 | 0.0519 | 0.0465 | 3/64" | 0.0469 | 1.19 | 81% | 0.00180 |
| #1-72 UNF | 72 | 0.0730 | 0.0640 | 0.0580 | #53 | 0.0595 | 1.51 | 75% | 0.00278 |
| #2-64 UNF | 64 | 0.0860 | 0.0759 | 0.0691 | #50 | 0.0700 | 1.78 | 79% | 0.00394 |
| #3-56 UNF | 56 | 0.0990 | 0.0874 | 0.0797 | #45 | 0.0820 | 2.08 | 73% | 0.00523 |
| #4-48 UNF | 48 | 0.1120 | 0.0985 | 0.0894 | #42 | 0.0935 | 2.37 | 68% | 0.00661 |
| #5-44 UNF | 44 | 0.1250 | 0.1102 | 0.1004 | #37 | 0.1040 | 2.64 | 71% | 0.00830 |
| #6-40 UNF | 40 | 0.1380 | 0.1218 | 0.1109 | #33 | 0.1130 | 2.87 | 77% | 0.0101 |
| #8-36 UNF | 36 | 0.1640 | 0.1460 | 0.1339 | #29 | 0.1360 | 3.45 | 78% | 0.0147 |
| #10-32 UNF | 32 | 0.1900 | 0.1697 | 0.1562 | #21 | 0.1590 | 4.04 | 76% | 0.0200 |
| #12-28 UNF | 28 | 0.2160 | 0.1928 | 0.1773 | #14 | 0.1820 | 4.62 | 73% | 0.0258 |
| 1/4-28 UNF | 28 | 0.2500 | 0.2268 | 0.2113 | #3 | 0.2130 | 5.41 | 80% | 0.0364 |
| 5/16-24 UNF | 24 | 0.3125 | 0.2854 | 0.2674 | I | 0.2720 | 6.91 | 75% | 0.0580 |
| 3/8-24 UNF | 24 | 0.3750 | 0.3479 | 0.3299 | Q | 0.3320 | 8.43 | 79% | 0.0878 |
| 7/16-20 UNF | 20 | 0.4375 | 0.4050 | 0.3834 | 25/64" | 0.3906 | 9.92 | 72% | 0.1187 |
| 1/2-20 UNF | 20 | 0.5000 | 0.4675 | 0.4459 | 29/64" | 0.4531 | 11.51 | 72% | 0.1599 |
| 9/16-18 UNF | 18 | 0.5625 | 0.5264 | 0.5024 | 33/64" | 0.5156 | 13.10 | 65% | 0.203 |
| 5/8-18 UNF | 18 | 0.6250 | 0.5889 | 0.5649 | 37/64" | 0.5781 | 14.68 | 65% | 0.256 |
| 3/4-16 UNF | 16 | 0.7500 | 0.7094 | 0.6823 | 11/16" | 0.6875 | 17.46 | 77% | 0.373 |
| 7/8-14 UNF | 14 | 0.8750 | 0.8286 | 0.7977 | 13/16" | 0.8125 | 20.64 | 67% | 0.509 |
| 1-12 UNF | 12 | 1.0000 | 0.9459 | 0.9098 | 59/64" | 0.9219 | 23.42 | 72% | 0.663 |
| 1-1/8-12 UNF | 12 | 1.1250 | 1.0709 | 1.0348 | 1-3/64" | 1.0469 | 26.59 | 72% | 0.856 |
| 1-1/4-12 UNF | 12 | 1.2500 | 1.1959 | 1.1598 | 1-11/64" | 1.1719 | 29.77 | 72% | 1.073 |
| 1-3/8-12 UNF | 12 | 1.3750 | 1.3209 | 1.2848 | 1-19/64" | 1.2969 | 32.94 | 72% | 1.315 |
| 1-1/2-12 UNF | 12 | 1.5000 | 1.4459 | 1.4098 | 1-27/64" | 1.4219 | 36.12 | 72% | 1.581 |
About the UNF series
A fine thread is shallower than the coarse thread of the same diameter, so the bolt has a larger core. 1/2-20 UNF has a stress area of 0.1599 in² against 0.1419 in² for 1/2-13 UNC, about 13% more. The smaller lead angle also resists loosening under vibration and gives finer adjustment.
The fine series ends at 1-1/2 in. Above that, ASME B1.1 continues it with the 12-thread series (12 UN). The thread sold as “1-14 UNF” is a common misnomer: the standard fine thread for 1 inch is 1-12, and 1-14 is a special (UNS) thread.
Threads per inch by series
Common questions
What is the tap drill for 1/4-28?
The tap drill for 1/4-28 UNF is a #3 drill, 0.2130 in (5.41 mm), for about 80% thread.
What is the tap drill for 10-32?
The tap drill for #10-32 UNF is a #21 drill, 0.1590 in (4.04 mm), for about 76% thread.
Is UNF stronger than UNC?
The bolt is stronger in tension, by roughly 10 to 15%, because its core is larger. The nut thread is more easily stripped in soft material, so coarse threads are preferred in aluminium and cast iron.
Other charts and tools
Sources: ASME B1.1 (series, basic dimensions and stress areas) and the tap drill tables of Machinery’s Handbook. How this site checks its data. Last reviewed 29 September 2026.