Hydraulic Fitting Sizes and Thread Table
If you do not know the size of the fitting in your hand, this page is all you need. Measure the outside diameter with a caliper, find it in the table, and compare metric, BSP, JIC and ORFS sizes side by side.
5 min read · 15-row dimension table · 4 frequently asked questions
How to work out the size yourself
You have a fitting in your hand and no idea what it is. Three steps get you there:
- Measure the outside diameter of the thread with a caliper. On a male part measure across the thread crests; on a female part measure across the roots.
- Establish the thread pitch. Without a thread gauge, count how many threads fall within 10 mm; metric pitch is given in millimetres (1.5 mm, say) while inch threads are given as threads per inch (19, say).
- Look at the end face. 24° cone → metric, 37° cone → JIC, flat face with an O-ring → ORFS, 60° internal cone or a flat face with a bonded seal → BSP.
If you cannot be certain, send us a photo of the part together with the caliper reading; we will identify the size and tell you the equivalent.
Metric DIN 2353 (24°) — L and S series
Metric fittings come in two series. The L series (light) is used on medium-pressure lines and the S series (heavy) on high-pressure lines. For the same tube diameter the S series has the larger thread — 10 mm tube, for example, is M16×1.5 in L series and M18×1.5 in S series. The two do not interchange.
Comparison thread table
Each row of the table below groups connection types of broadly similar capacity. Note: this is not a "these will screw together" table; it is there to show relative sizes across types.
Sizes that get confused
- M22×1.5 appears both as 15L and as 14S. The cone diameters differ; separate them by looking at the tube diameter.
- G 1/4" (BSP) and 1/4" NPT look similar but do not fit: BSP is 55° and NPT is 60° and tapered. Forcing them ruins both parts.
- M16×1.5 is 10L in metric fittings, but corresponds to 8S in the S series.
Hose size and fitting size are not the same thing
Hose size is quoted by inner diameter (DN12, 1/2" and so on), fitting size by thread diameter. A 1/2" hose can take an M22×1.5 end just as easily as a 3/4"-16 JIC end. State the two separately — for example: "1/2" 2SN hose, one end 3/4-16 JIC female, other end M22×1.5 15L straight".
Metric – BSP – JIC – ORFS comparison thread table
| Tube / hose | Metric L (24°) | Metric S (24°) | BSP (G) | JIC (37°) | ORFS |
|---|---|---|---|---|---|
| 6 mm / 1/4" | M12×1.5 (6L) | M14×1.5 (6S) | G 1/8" | 7/16" – 20 | 9/16" – 18 |
| 8 mm / 5/16" | M14×1.5 (8L) | M16×1.5 (8S) | G 1/4" | 1/2" – 20 | 11/16" – 16 |
| 10 mm / 3/8" | M16×1.5 (10L) | M18×1.5 (10S) | G 1/4" | 9/16" – 18 | 11/16" – 16 |
| 12 mm / 1/2" | M18×1.5 (12L) | M20×1.5 (12S) | G 3/8" | 3/4" – 16 | 13/16" – 16 |
| 15 mm / 1/2" | M22×1.5 (15L) | M22×1.5 (14S) | G 1/2" | 3/4" – 16 | 13/16" – 16 |
| 16 mm / 5/8" | — | M24×1.5 (16S) | G 1/2" | 7/8" – 14 | 1" – 14 |
| 18 mm / 3/4" | M26×1.5 (18L) | — | G 1/2" | 1.1/16" – 12 | 1.3/16" – 12 |
| 20 mm / 3/4" | — | M30×2 (20S) | G 3/4" | 1.1/16" – 12 | 1.3/16" – 12 |
| 22 mm / 3/4" | M30×2 (22L) | — | G 3/4" | 1.1/16" – 12 | 1.3/16" – 12 |
| 25 mm / 1" | — | M36×2 (25S) | G 1" | 1.5/16" – 12 | 1.7/16" – 12 |
| 28 mm / 1" | M36×2 (28L) | — | G 1" | 1.5/16" – 12 | 1.7/16" – 12 |
| 30 mm / 1.1/4" | — | M42×2 (30S) | G 1.1/4" | 1.5/8" – 12 | 1.11/16" – 12 |
| 35 mm / 1.1/4" | M45×2 (35L) | — | G 1.1/4" | 1.5/8" – 12 | 1.11/16" – 12 |
| 38 mm / 1.1/2" | — | M52×2 (38S) | G 1.1/2" | 1.7/8" – 12 | 2" – 12 |
| 42 mm / 1.1/2" | M52×2 (42L) | — | G 1.1/2" | 1.7/8" – 12 | 2" – 12 |
The table scrolls horizontally. Values are for guidance; we recommend confirming the size before ordering.
Frequently Asked Questions
How do I identify a fitting size?
You need three pieces of information: the outside diameter of the thread (measured with a caliper), the thread pitch (millimetres for metric, threads per inch for inch sizes) and the shape of the end face (24° cone, 37° cone, flat face with O-ring, or bonded seal). With those three the size is settled.
What size is M22x1.5?
In metric DIN 2353 fittings M22×1.5 covers two sizes: 15L (15 mm tube) in the L series and 14S (14 mm tube) in the S series. Which one you have is determined by the tube diameter or the cone diameter.
Do L series and S series fittings interchange?
No. For the same tube diameter the thread sizes differ — on 10 mm tube L series is M16×1.5 while S series is M18×1.5. The S series is for higher pressure and will not fit an L series connection.
Is hose size the same as fitting size?
No. Hose size is quoted by inner diameter (DN12, 1/2" and so on) while fitting size is quoted by thread diameter. When ordering, state both separately: hose size, reinforcement class and the fitting type at each end.