AN Fitting Size Chart
Look up 37° flare dash sizes -2 to -32 with tube size, thread and pipe size, or measure a male thread and find which dash size it is.
Identify a fitting by measuring its male thread
Use calipers across the thread crests.
Then confirm with a thread pitch gauge: the threads per inch must match too.
Closest 37° flare size
-6 (9/16-18)
Measured 0.56 in vs 0.5625 in nominal · next closest -5 (1/2-20)
| Tube O.D. | 3/8 in |
| Threads per inch | 18 |
| Nominal pipe size | 1/4 in |
What this page cannot tell you
Whether a fitting is AN (military), JIC or another 37° flare part, or whether it's a 45° SAE flare, which looks similar. Pressure ratings shown are one maker's figures for its 316 stainless fittings and depend on material, tube and assembly. A worn thread measures small; check the pitch as well as the diameter.
37° flare (SAE J514) dash size chart
| Dash | Tube O.D. (in) | Thread | Pipe size (in) | psi union/bulkhead | psi with pipe thread |
|---|---|---|---|---|---|
| -2 | 1/8 | 5/16-24 | 1/8 | 5,000 | 5,000 |
| -3 | 3/16 | 3/8-24 | 1/8 | 5,000 | 5,000 |
| -4 | 1/4 | 7/16-20 | 1/8 | 5,000 | 5,000 |
| -5 | 5/16 | 1/2-20 | 1/8 | 5,000 | 5,000 |
| -6 | 3/8 | 9/16-18 | 1/4 | 5,000 | 5,000 |
| -8 | 1/2 | 3/4-16 | 3/8 | 4,500 | 4,000 |
| -10 | 5/8 | 7/8-14 | 1/2 | 3,500 | 3,000 |
| -12 | 3/4 | 1-1/16-12 | 3/4 | 3,500 | 3,000 |
| -14 | 7/8 | 1-3/16-12 | 3/4 | 3,000 | 2,500 |
| -16 | 1 | 1-5/16-12 | 1 | 3,000 | 2,000 |
| -20 | 1-1/4 | 1-5/8-12 | 1-1/4 | 2,500 | 1,150 |
| -24 | 1-1/2 | 1-7/8-12 | 1-1/2 | 2,000 | 1,000 |
| -32 | 2 | 2-1/2-12 | 2 | 1,500 | 1,000 |
Pressure columns are Ham-Let’s ratings for its stainless fittings; the catalog says they “should not be construed as guaranteed minimum”.
How to identify an AN or 37° flare fitting size
- Measure the male thread. Outside diameter across the thread crests, with calipers.
- Enter it. In inches or millimetres.
- Read the closest dash size. And the next closest, in case the thread is worn.
- Confirm the pitch. Check threads per inch with a pitch gauge against the chart.
10 situations where an AN fitting size chart helps
Fuel line plumbing
Match a -6 or -8 line to the right fittings and adapters.
Identifying an unknown fitting
Measure the thread and find the dash size.
Buying adapters
Know the thread on each end before ordering.
Oil cooler and turbo lines
Dash sizes for oil feed and return.
Brake lines
Small sizes like -3 and -4.
Hydraulic tube work
37° flare (SAE J514) is common on hydraulic systems.
Converting to pipe thread
The chart lists the nominal pipe size used with each dash size.
Checking pressure ratings
One maker's working pressures for each size.
Metric measurements
Enter millimetres from metric calipers.
Telling 37° from 45° flare
If nothing matches, the fitting may be a different flare system.
Where the chart comes from
The table is Table 2 of Ham-Let's 'SAE37 Flare 3-Piece Tube Assembly' catalog (2025), whose fittings are described as 'compliant with SAE J514 standard'. It lists, for each nominal SAE dash size, the nominal tube outside diameter, the 37° flare straight thread, the nominal pipe size, and Ham-Let's allowable working pressures for union and bulkhead fittings and for fittings with pipe threads. Values are copied as printed.
The dash number is the tube's outside diameter in sixteenths of an inch: -6 is 6/16 = 3/8 in tube. The identifier compares a measured thread diameter with the nominal major diameter of each thread in the table.
Limits: the pressure ratings are one manufacturer's figures for its 316/316L stainless steel fittings, and the catalog itself says they 'should not be construed as guaranteed minimum'. AN (military) parts are specified in separate documents; check your parts' specifications where it matters. A 45° SAE flare fitting can share a thread size with a 37° part but will not seal against it. Everything runs in your browser.
Sources
- Ham-Let — SAE37 Flare 3-Piece Tube Assembly catalog (SAE J514) — Table 2: dash size, tube O.D., thread, pipe size, pressure
Frequently asked questions
What thread is -6 AN?
In the SAE J514 37° flare table used here, -6 is 9/16-18 for 3/8 in tube.
What does the dash number mean?
Tube outside diameter in sixteenths of an inch: -8 = 8/16 = 1/2 in.
What thread is -8?
3/4-16 for 1/2 in tube.
How do I measure an AN fitting?
Measure the outside diameter of the male thread with calipers, then confirm threads per inch with a pitch gauge.
Are AN and JIC the same?
Both are 37° flare systems with the same dash sizes. Military AN parts have their own specifications, so check yours where it matters.
Can I connect a 37° fitting to a 45° flare?
No. The flare angles don't seal against each other even when the threads match.
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