# Threaded rod, inch: #4 to 4 in, UNC and UNF threads per inch, major diameter in inches and mm, standard lengths

> What are the threads per inch and diameter of 1/4, 3/8, 1/2 and 5/8 inch threaded rod?

- Category: Hardware › Fasteners
- Kind: Standard part
- Basis: ASME B18.31.3 as summarised by Torqbolt (sizes, TPI) and fasten.it (lengths); numbers only
- Page: https://xemstudio.com/objects/threaded-rod-inch-unc-unf-sizes/ · JSON: https://xemstudio.com/api/geometry?object=threaded-rod-inch-unc-unf-sizes · Plain text: https://xemstudio.com/objects/threaded-rod-inch-unc-unf-sizes/sheet.txt
- License: dimension sheet CC BY 4.0 (Xem Studio); files CC BY 4.0 or their publisher's license
- Use in every chat: add https://xemstudio.com/mcp as a connector (https://xemstudio.com/use-with-ai/)

**Exact dimensions.** Every file is drawn at true size with no tolerance added. The holes and pins that meet another part are listed below under Mating features, with the fit each joint needs; open those by your process's clearance before making the part.

## Notes

- Inch threaded rod (studding, all-thread; ASME B18.31.3) is cut from stock in the UNC (coarse) or UNF (fine) series. Sizes and threads per inch are from Torqbolt's B18.31.3 summary. Its 7/16 row prints 0.4370 in; the fraction 7/16 is 0.4375 in and that is shown. The second source's table (fasten.it) lists the UNC and UNF numbers one row out of step for the fractional sizes (its UNC column reads 18 for 1/4 where Torqbolt has 20, and 16 for 5/16 where Torqbolt has 18), so its TPI numbers are not used.
- Nominal diameter is the major diameter of the thread; the major diameter limits that the standard prints were not on a page that could be read. No file is added: a rod is a plain cylinder (Xem draws threads as plain cylinders at the major diameter) and carries no more than the number.
- Lengths: ASME B18.31.3 says rods are normally produced in, but not limited to, 3 ft, 6 ft, 10 ft and 12 ft; length tolerance is ±1/2 in for nominal lengths of 6 ft and longer and ±1/4 in under 6 ft (fasten.it's B18.31.3 page). Cut-to-length rods are common.
- Metric rod (DIN 976, M3 to M12) is on the threaded-rod-metric-din-976 page. Left out: thread class limits, minor and pitch diameters, mechanical grades (A307, B7, 18-8) and the UNS-size 1-14 for 1 in UNF.

## Mating features (exact size; open press / slide / run / socket by your process clearance, leave designed and clamp as drawn)

| feature | exact | mates with | fit | files |
|---|---|---|---|---|
| 1/4-20 rod | major diameter 6.35, 20 TPI (pitch 1.27 computed) | 1/4-20 UNC nut or tapped hole (see hex-nuts-inch) | designed | all |
| 3/8-16 rod | major diameter 9.525, 16 TPI (pitch 1.5875 computed) | 3/8-16 UNC nut or tapped hole | designed | all |
| 1/2-13 rod | major diameter 12.7, 13 TPI (pitch 1.954 computed) | 1/2-13 UNC nut or tapped hole | designed | all |

## Sizes

| size | nominal major diameter (in) | major diameter (mm, computed) | UNC | UNC pitch (mm, computed 25.4 ÷ TPI) | UNF |
|---|---|---|---|---|---|
| #4 | 0.1120 | 2.84 | 4-40 | 0.635 | 4-48 |
| #5 | 0.1250 | 3.17 | 5-40 | 0.635 | 5-44 |
| #6 | 0.1380 | 3.51 | 6-32 | 0.794 | 6-40 |
| #8 | 0.1640 | 4.17 | 8-32 | 0.794 | 8-36 |
| #10 | 0.1900 | 4.83 | 10-24 | 1.058 | 10-32 |
| #12 | 0.2160 | 5.49 | 12-24 | 1.058 | 12-28 |
| 1/4 | 0.2500 | 6.35 | 1/4-20 | 1.270 | 1/4-28 |
| 5/16 | 0.3125 | 7.94 | 5/16-18 | 1.411 | 5/16-24 |
| 3/8 | 0.3750 | 9.52 | 3/8-16 | 1.587 | 3/8-24 |
| 7/16 | 0.4375 | 11.11 | 7/16-14 | 1.814 | 7/16-20 |
| 1/2 | 0.5000 | 12.70 | 1/2-13 | 1.954 | 1/2-20 |
| 9/16 | 0.5625 | 14.29 | 9/16-12 | 2.117 | 9/16-18 |
| 5/8 | 0.6250 | 15.88 | 5/8-11 | 2.309 | 5/8-18 |
| 3/4 | 0.7500 | 19.05 | 3/4-10 | 2.540 | 3/4-16 |
| 7/8 | 0.8750 | 22.22 | 7/8-9 | 2.822 | 7/8-14 |
| 1 | 1.0000 | 25.40 | 1-8 | 3.175 | 1-12 (the source also prints 1-14 UNS) |
| 1-1/8 | 1.1250 | 28.57 | 1-1/8-7 | 3.629 | 1-12 |
| 1-1/4 | 1.2500 | 31.75 | 1-1/4-7 | 3.629 | 1-12 |
| 1-3/8 | 1.3750 | 34.92 | 1-3/8-6 | 4.233 | 1-12 |
| 1-1/2 | 1.5000 | 38.10 | 1-1/2-6 | 4.233 | 1-12 |
| 1-3/4 | 1.7500 | 44.45 | 1-3/4-5 | 5.080 | - |
| 2 | 2.0000 | 50.80 | 2-4.5 | 5.644 | - |
| 2-1/4 | 2.2500 | 57.15 | 2-1/4-4.5 | 5.644 | - |
| 2-1/2 | 2.5000 | 63.50 | 2-1/2-4 | 6.350 | - |
| 2-3/4 | 2.7500 | 69.85 | 2-3/4-4 | 6.350 | - |
| 3 | 3.0000 | 76.20 | 3-4 | 6.350 | - |
| 3-1/4 | 3.2500 | 82.55 | 3-1/4-4 | 6.350 | - |
| 3-1/2 | 3.5000 | 88.90 | 3-1/2-4 | 6.350 | - |
| 3-3/4 | 3.7500 | 95.25 | 3-3/4-4 | 6.350 | - |
| 4 | 4.0000 | 101.60 | 4-4 | 6.350 | - |

## Where the files are

- Torqbolt: [ASME B18.31.3 threaded rods: nominal diameters and UNC / UNF threads per inch, #4 to 5 in](https://torqbolt.com/asme-b18-31-3-threaded-rods-dimensions-standards-specifications) — web — Publisher's page; dimensions are facts
- fasten.it: [ASME B18.31.3 Standard dimensions for threaded rods, inch series: normal lengths 3, 6, 10, 12 ft and length tolerance](https://fasten.it/norms/norm/asme_b18.31.3) — web — Publisher's page; dimensions are facts

## Questions

**How many threads per inch is 1/4 threaded rod?**

20 (1/4-20 UNC), or 28 (1/4-28 UNF).

**What is the diameter of 1/2-13 threaded rod in mm?**

12.7 mm major diameter, 13 threads per inch (pitch 1.954 mm computed).

**What lengths does threaded rod come in?**

Normally 3, 6, 10 and 12 ft, tolerance ±1/2 in for 6 ft and longer and ±1/4 in below 6 ft (ASME B18.31.3).

**What is 3/8-16 threaded rod?**

3/8 in (9.525 mm) coarse thread, 16 TPI (pitch 1.588 mm computed).

## Fits with

- [Threaded rod, metric M3 to M12 (DIN 976), 100 to 1000 mm](https://xemstudio.com/objects/threaded-rod-metric-din-976/)
- [Threaded rod, metric: M4 × 194.2](https://xemstudio.com/objects/threaded-rods-metric/)
- [Hex nuts, inch: #4-40 to 3/4-10 (ASME B18.2.2)](https://xemstudio.com/objects/hex-nuts-inch/)
- [Nylon-insert lock nuts, inch (ASME B18.16.6): 1/4 to 1-1/2 width across flats, across corners, height](https://xemstudio.com/objects/nylon-insert-lock-nuts-inch-asme-b18-16-6/)
- [Bar stock sizes: 1018 steel round and square 1/8 to 6 in, 6061 aluminum square 1/4 to 8 in (distributor list, inches and mm)](https://xemstudio.com/objects/bar-stock-sizes-round-square-steel-aluminum/)
- [Strut channel nuts (spring nuts) for 1-5/8 in channel: threads, thickness and loads](https://xemstudio.com/objects/strut-channel-spring-nuts/)