Measured-thread lookup
Find a JIC Size From Thread Measurements
Enter the male external-thread major diameter and confirm the thread pitch.
Default example: a 0.750 in male thread OD with 16 TPI matches nominal JIC -8, 3/4-16 UNF, for 1/2 in tube OD. Confirm the 37° seat before use.
Identification limit
A nearest nominal size is not proof of compatibility. Confirm TPI, a 37° seat, fitting standard, gender, condition, material, pressure rating, and manufacturer requirements. Straight threads retain the connection; the flare seats create the seal.
Measurement locations
How to Identify the JIC Thread and 37° Seat
The diagram separates the retaining thread from the metal-to-metal sealing interface.
- Male fitting
- Metal-to-metal sealing interface
- Female fitting and connected tube
- Selected dash size
- -8
- Thread
- 3/4-16 UNF
- Nominal diameter D
- 0.7500 in · 19.05 mm
- Nominal tube OD
- 1/2 in · 12.70 mm
- Sealing surface
- 37° metal seats
13-size cross-reference
JIC 37° Flare Dash Size and Thread Chart
Cross-reference dash size, tube OD, unified thread, TPI, nominal male-thread diameter, and metric pitch.
Search by dash size, fraction, decimal, metric size, thread designation, TPI, UN, or UNF. Use Select to synchronize the result and diagram.
No JIC sizes match these table filters. Clear the search or TPI filter; do not infer a nonlisted dash size.
Scroll horizontally to view additional columns and vertically to view additional rows. Column headers and the dash-size column remain visible while scrolling.
| Select | Size | Thread identification | |||||||
|---|---|---|---|---|---|---|---|---|---|
| Family | |||||||||
| -2 | 1/8 | 3.18 | 5/16-24 UNF | UNF | 24 | 5/16 (0.3125) | 7.94 | 1.058 | |
| -3 | 3/16 | 4.76 | 3/8-24 UNF | UNF | 24 | 3/8 (0.3750) | 9.53 | 1.058 | |
| -4 | 1/4 | 6.35 | 7/16-20 UNF | UNF | 20 | 7/16 (0.4375) | 11.11 | 1.270 | |
| -5 | 5/16 | 7.94 | 1/2-20 UNF | UNF | 20 | 1/2 (0.5000) | 12.70 | 1.270 | |
| -6 | 3/8 | 9.53 | 9/16-18 UNF | UNF | 18 | 9/16 (0.5625) | 14.29 | 1.411 | |
| -8 | 1/2 | 12.70 | 3/4-16 UNF | UNF | 16 | 3/4 (0.7500) | 19.05 | 1.588 | |
| -10 | 5/8 | 15.88 | 7/8-14 UNF | UNF | 14 | 7/8 (0.8750) | 22.23 | 1.814 | |
| -12 | 3/4 | 19.05 | 1-1/16-12 UN | UN | 12 | 1-1/16 (1.0625) | 26.99 | 2.117 | |
| -14 | 7/8 | 22.23 | 1-3/16-12 UN | UN | 12 | 1-3/16 (1.1875) | 30.16 | 2.117 | |
| -16 | 1 | 25.40 | 1-5/16-12 UN | UN | 12 | 1-5/16 (1.3125) | 33.34 | 2.117 | |
| -20 | 1-1/4 | 31.75 | 1-5/8-12 UN | UN | 12 | 1-5/8 (1.6250) | 41.28 | 2.117 | |
| -24 | 1-1/2 | 38.10 | 1-7/8-12 UN | UN | 12 | 1-7/8 (1.8750) | 47.63 | 2.117 | |
| -32 | 2 | 50.80 | 2-1/2-12 UN | UN | 12 | 2-1/2 (2.5000) | 63.50 | 2.117 | |
Nominal thread diameter is an identification reference, not an acceptance tolerance. Actual measurements can differ because of manufacturing tolerance, coating, wear, damage, and technique. Do not infer unlisted dash sizes.
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How to Measure a JIC Fitting
- Make the system safe. Shut down, isolate, and fully depressurize the equipment using the manufacturer’s procedure. Never loosen a connection to test whether pressure remains.
- Clean and inspect the fitting. Remove contamination that could hide the thread crests or seat. Stop if the threads or flare surface are damaged.
- Measure the male thread OD. Place caliper jaws across the external thread crests. Do not measure the wrench hex or assume the tube OD equals the thread diameter.
- Determine TPI. Match a thread-pitch gauge to the threads. The same approximate diameter can occur in different connection systems.
- Confirm the sealing geometry. Verify straight unified threads and a 37° flare seat with the correct gauge or manufacturer documentation.
Measurement reality
A caliper reading may fall slightly above or below nominal because of tolerance, plating, wear, damage, dirt, and measuring angle. Use the finder as an identification clue, then verify the full connection.
How JIC Dash Sizes Relate to Tube OD
For the fitting-end crosswalk on this page, the dash number represents nominal tube outside diameter in sixteenths of an inch. A -8 JIC end corresponds to 8/16 in, or 1/2 in, nominal tube OD. A -12 end corresponds to 12/16 in, or 3/4 in.
Dash size does not directly state thread diameter. An adapter or hose-end part number can also contain different dash sizes for its two ends, so confirm which end the designation describes.
Why Thread Size Alone Cannot Confirm JIC
JIC uses straight threads to draw the connection together, but the primary seal occurs where the mating 37° metal seats contact. A look-alike connection may accept several turns of thread yet use a different seat angle, thread form, or sealing method.
JIC Versus Common Look-Alike Connections
| Connection | Primary identifying feature | Sealing location | Compatibility caution |
|---|---|---|---|
| JIC | 37° flare with straight unified threads | Mating 37° metal seats | Verify thread, pitch, seat angle, and governing specification. |
| SAE 45° flare | 45° flare seat | Mating 45° seats | Do not mate to JIC solely because threads appear to match. |
| AN | 37° flare geometry under a different application specification | Mating 37° seats | Verify specification, tolerances, material, qualification, and application. |
| SAE ORB | Straight thread with an O-ring at the port | O-ring | Matching thread does not make an ORB port a JIC flare connection. |
| JIS 30° | 30° seat; thread family depends on type | Mating 30° seats | Seat angle differs from JIC. |
| BSP | Whitworth thread form; parallel or tapered variants | Varies by connection | Thread form and sealing method differ. |
| NPT | Tapered pipe thread | Thread interference with approved sealant | Not a straight-thread 37° flare connection. |
JIC Size Identification Examples
Example 1: 0.750 in and 16 TPI
Assumption: The external male thread measures 0.750 in and a gauge confirms 16 TPI.
The 16-TPI candidates are filtered first. The listed nominal diameter is 0.7500 in for JIC -8, so the measurement difference is 0.0000 in.
Interpretation: The nearest nominal row is -8, 3/4-16 UNF, for 1/2 in tube OD. Confirm the 37° seat and manufacturer requirements before treating it as JIC.
Example 2: 26.99 mm and 12 TPI
Assumption: The male thread OD is 26.99 mm and the pitch gauge confirms 12 TPI.
26.99 mm ÷ 25.4 = 1.0626 in. The nearest 12-TPI nominal diameter is 1.0625 in for JIC -12, a difference of about 0.0025 mm.
Interpretation: The nearest nominal row is -12, 1-1/16-12 UN, for 3/4 in tube OD. This still does not prove the seat angle, standard, or product suitability.
Selection and Assembly Limitations
This chart identifies nominal fitting-end size. It does not determine material compatibility, tube wall thickness, flare quality, assembly torque, working pressure, temperature limit, vibration suitability, or hose-to-fitting compatibility.
- Use product-specific manufacturer instructions for inspection, assembly, torque, and pressure rating.
- Replace damaged threads or sealing surfaces; do not force mismatched connections together.
- Do not put thread tape on the JIC flare-sealing interface. The metal seats—not the straight threads—form the primary seal.
- Never work on a pressurized hydraulic system.
Standards, Scope, and Data Method
Source basis checked August 10, 2026 · dataset T2E-JIC-CROSSWALK-2026-08-10
This independently arranged identification crosswalk is limited to 13 listed JIC 37° flare sizes. Dash-to-tube mappings and unified-thread designations were checked against the cited standards scope and public manufacturer identification material. Metric dimensions and pitch are calculated from the inch values without intermediate rounding.
- SAE J514/1_202211 — Metallic Connections for Fluid Power and General Use—Part 1: 37 Degree Flared FittingsOfficial November 2022 scope record for SAE 37° flared fittings. Copyrighted standard; cited and summarized, not reproduced.
- ISO 8434-2:2007 — Metallic tube connections—Part 2: 37° flared connectorsOfficial Edition 2 scope and lifecycle record. Its 6–50.8 mm tube-OD scope does not classify the smaller SAE rows on this page as ISO sizes. ISO/FDIS 8434-2 Edition 3 was in final approval when checked.
- Brennan Industries Thread ChartsPublic manufacturer reference used to cross-check the limited dash-size, tube-OD, and JIC-thread mapping; the PDF layout and unrelated tables are not reproduced.
- Dixon: JIC vs. SAE Flare FittingsIdentification guidance supporting verification of thread, pitch, and seat angle and the warning against assuming 37° and 45° flare compatibility.
Dataset and Source-Check Details
- Source-controlled fields
- Dash size, nominal tube OD, unified thread designation, thread family, and TPI
- Calculated fields
- Millimetres = inches × 25.4; pitch = 25.4 ÷ TPI
- Included range
- JIC -2 through -32; only the 13 explicitly listed rows
- Excluded
- Pressure, torque, tolerances, hex dimensions, hose-ID equivalence, material, and unlisted dash sizes
- Rights decision
- Limited transformed factual crosswalk with citations; no standards figures, full standards tables, or CSV redistribution
- Publisher
- Turn2Engineering
JIC Fitting Size FAQs
A -6 JIC fitting uses a 9/16-18 UNF thread and corresponds to 3/8 in nominal tube OD. Confirm that the connection also has the required 37° flare seat.
No. The straight threads retain and load the joint; the mating 37° metal seats form the primary seal.
Do not treat them as interchangeable. Their sealing angles differ. Use a connection only when the specific component manufacturer identifies it as suitable for both seats and the application requirements are met.
No automatic interchangeability should be assumed. Even when the 37° geometry appears compatible, verify the governing specification, tolerances, material, qualification, and application requirements.
Use a thread-pitch gauge and an appropriate verified male reference or manufacturer data, then confirm the internal 37° seat. An approximate female inside-diameter measurement is not definitive.
Use the Chart as an Identification Check
Start with measured male thread OD and exact TPI, find the nearest nominal row, and then confirm the 37° seat and product requirements. The chart narrows the likely size; it does not approve compatibility, assembly, or pressure service.