JIC Fittings Guide › JIC Thread Size Chart
JIC Thread Size Chart (-2 to -32)
This chart lists every standard JIC 37° flare size from -2 to -32 with its UNF/UN thread, threads per inch (TPI), approximate male thread OD in inches and millimeters, and approximate female thread ID. Thread sizes follow SAE J514; measured OD/ID values are approximate and drawn from published hydraulic identification guides. For identification methods and comparisons, see the main JIC fittings guide.
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Full JIC Thread Size Chart
| Dash | Tube OD | Thread (UNF/UN) | TPI | Male thread OD (in) | Male thread OD (mm) | Female thread ID (approx.) |
|---|---|---|---|---|---|---|
| -2 | 1/8" | 5/16-24 UNF | 24 | 0.31" | 7.9 | 9/32 (0.27") |
| -3 | 3/16" | 3/8-24 UNF | 24 | 0.38" | 9.5 | 11/32 (0.34") |
| -4 | 1/4" | 7/16-20 UNF | 20 | 0.44" | 11.1 | 13/32 (0.39") |
| -5 | 5/16" | 1/2-20 UNF | 20 | 0.50" | 12.7 | 15/32 (0.45") |
| -6 | 3/8" | 9/16-18 UNF | 18 | 0.56" | 14.3 | 17/32 (0.51") |
| -8 | 1/2" | 3/4-16 UNF | 16 | 0.75" | 19.1 | 11/16 (0.69") |
| -10 | 5/8" | 7/8-14 UNF | 14 | 0.88" | 22.2 | 13/16 (0.81") |
| -12 | 3/4" | 1-1/16-12 UN | 12 | 1.06" | 27.0 | 1 (0.98") |
| -14 | 7/8" | 1-3/16-12 UN | 12 | 1.19" | 30.2 | 1-1/8 (1.10") |
| -16 | 1" | 1-5/16-12 UN | 12 | 1.31" | 33.3 | 1-1/4 (1.23") |
| -20 | 1-1/4" | 1-5/8-12 UN | 12 | 1.63" | 41.3 | 1-9/16 (1.54") |
| -24 | 1-1/2" | 1-7/8-12 UN | 12 | 1.88" | 47.6 | 1-13/16 (1.79") |
| -32 | 2" | 2-1/2-12 UN | 12 | 2.50" | 63.5 | 2-7/16 (2.42") |
Male OD mm values are inch nominal × 25.4, rounded. Female ID values are approximate measurements across thread crests as published in McGill Hose's Fluid Ports & Connectors Identification Guide. Measured values on worn or plated parts may differ slightly.
How to Read the Chart
Dash size
The dash number is the tube OD in sixteenths of an inch. A -6 fits 6/16" = 3/8" tube; a -12 fits 12/16" = 3/4" tube. For hose, the dash number usually refers to the hose inside diameter in sixteenths, and the hose end is matched to a JIC fitting of the same dash.
Thread designation
A thread such as 3/4-16 UNF means 3/4" nominal major diameter and 16 threads per inch. Sizes -2 through -10 use fine-series UNF threads. From -12 up, JIC uses a constant 12 TPI on the UN (unified) 12-pitch series.
Thread is bigger than tube
The thread is always larger than the tube it serves. A -8 fitting is for 1/2" tube but has a 3/4" thread. Confusing the two is the most common ordering error.
Quick Reference by TPI
| TPI | JIC sizes |
|---|---|
| 24 | -2 (5/16), -3 (3/8) |
| 20 | -4 (7/16), -5 (1/2) |
| 18 | -6 (9/16) |
| 16 | -8 (3/4) |
| 14 | -10 (7/8) |
| 12 | -12, -14, -16, -20, -24, -32 |
Two sizes share each of the 24 and 20 TPI pitches, and six sizes share 12 TPI, so always measure the diameter as well as the pitch.
Most Common Sizes
-4, -6, -8, -12 and -16 are the most commonly stocked JIC sizes. Odd sizes -3, -5 and -14 are less common and can have longer lead times, so confirm availability when quoting.
Sizes That Overlap Other Fitting Types
- SAE 45° flare: In sizes -2, -3, -4, -5, -8 and -10, JIC and SAE 45° flare share the same thread but have different seat angles. Use a seat gauge.
- SAE O-ring boss (ORB): ORB ports use the same thread sizes as JIC at each dash size (per Swagelok's identification guide). The ORB male has an O-ring behind the threads instead of a 37° nose.
- ORFS: ORFS threads are one step larger, e.g. -8 ORFS is 13/16-16. A -6 JIC and -4 ORFS both use 9/16-18. See JIC vs ORFS.
- AN: AN fittings use identical threads at each dash size but a tighter thread class. See JIC vs AN.
- NPT: NPT is tapered with different pitches; see JIC vs NPT.
Measuring Against the Chart
- Measure the male thread OD across the crests (or female ID across the inner crests) with calipers.
- Count TPI with an inch pitch gauge.
- Find the row matching both values.
- Confirm the 37° seat with a seat angle gauge.
Full instructions: How to identify a JIC fitting.
Standards Behind the Chart
JIC 37° flare fittings are specified by SAE J514 in North America and ISO 8434-2 internationally. Thread sizes in this chart match those listed for SAE 37° flare in Swagelok's Thread and End Connection Identification Guide and in hydraulic distributor thread guides. Pressure ratings vary by size, material and manufacturer, so check the supplier's catalog for working pressure rather than relying on a generic figure.
Ordering Using the Chart
When requesting a quote, give the dash size of each end (e.g. -12 JIC male × -12 ORB male), the configuration, material and quantity. If you are not sure of the size, choose "Not sure" in the form and describe your measurements in the notes field.
Inch to Metric Conversion Notes
JIC is an inch-based system, but many technicians measure in millimeters. The mm column above is simply the nominal inch thread diameter multiplied by 25.4. A digital caliper reading of roughly 19 mm on a male thread with 16 TPI therefore points to a 3/4-16 (-8) JIC. Do not confuse a JIC thread with a metric fine thread of similar diameter: metric threads are specified by pitch in millimeters (for example M18×1.5), and an inch pitch gauge will not sit cleanly on them. If neither your inch nor your metric gauge seats perfectly, re-measure before ordering.
Tube and Hose Sizing Tips
For tube, measure the outside diameter of the tube itself; the dash size is that OD in sixteenths. For hose, the dash number generally relates to the hose inside diameter, and the crimped hose end is selected for the hose and the JIC end separately — a -8 hose can carry a -8 JIC female swivel, or a different JIC size through a reducing end. When in doubt, quote the hose part number printed on the layline along with the fitting sizes you need.
FAQ
What thread is a -6 JIC?
A -6 JIC uses a 9/16-18 UNF thread and fits 3/8" OD tube. Male thread OD measures about 0.56" (14.3 mm).
What thread is a -12 JIC?
A -12 JIC uses a 1-1/16-12 UN thread for 3/4" OD tube. Male OD is about 1.06" (27.0 mm).
What thread is a -16 JIC?
A -16 JIC uses a 1-5/16-12 UN thread for 1" OD tube. Male OD is about 1.31" (33.3 mm).
Why is the JIC thread larger than the tube size?
The dash size refers to tube OD, while the thread must be larger to fit around the tube and flare. A -8 is for 1/2" tube but uses a 3/4-16 thread.
Which JIC sizes use 12 threads per inch?
-12, -14, -16, -20, -24 and -32 all use 12 TPI UN threads.
Do JIC and SAE O-ring boss share threads?
Yes, ORB ports use the same thread sizes as JIC at each dash size, but ORB seals with an O-ring rather than a 37° flare.
What standard defines JIC thread sizes?
SAE J514 (and ISO 8434-2 internationally) defines the 37° flare fitting, including its UNF/UN thread sizes.
Related guides
- JIC Fittings Guide (main)
- JIC vs NPT
- JIC vs ORFS
- JIC vs AN
- How to Identify a JIC Fitting
- -4 JIC Fittings
- -6 JIC Fittings
- -8 JIC Fittings
- -10 JIC Fittings
- -12 JIC Fittings
- -16 JIC Fittings
- JIC vs SAE 45° Flare
- JIC vs BSPP
- JIC vs Metric (DIN 24°)
- JIC Torque Specs
- JIC Fitting Types
- JIC Materials & Pressure Ratings
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