How to Measure Hydraulic Fittings: A 5-Step Guide

Tuesday, February 25, 2025

Measuring hydraulic fittings correctly is essential for ensuring a secure and leak-free connection in your hydraulic systems. Whether you're working on a large industrial machine or a smaller custom setup, understanding how to measure hydraulic fittings is a crucial step to get the right size and type for your application. 

In this guide, we'll walk you through a simple 5-step process for measuring hydraulic fittings, ensuring accuracy, and explaining the key dimensions to consider.

Step 1: Understand the Types of Hydraulic Fittings

Before diving into the measurements, it's important to note that there are several types of hydraulic fitting termination ends. Some of the most common types include:

• ORFS (O-Ring Face Seal) fittings

• JIC 37° (Joint Industry Council) fittings

• NPT (National Pipe Thread) fittings (Parallel & Tapered)

• BSP (British Standard Pipe) fittings

• Adjustable and non-adjustable straight thread ends (Inch & Metric)

Each fitting type may have different measurement methods, so it's important to know which type you're working with. 

To better understand these fitting types and how to measure them, be sure to check out our Hydraulic Fittings Guide, where we explain their features, uses, and proper measurements.

Step 2: Measure the Thread Size

The most critical measurement for hydraulic fittings is the thread size. This is important because a mismatched thread size can cause leaks, reduced performance, or even system failure.

To measure the thread size, you'll need a caliper or thread gauge. Here's what you need to do:

1. Measure the outer diameter of the thread with your caliper.

2. For thread pitch, fittings with inch threads such as NPTF (pipe), JIC or ORFS, count the threads per inch (TPI).  For metric threads the designation is millimeters per thread.

Examples: 

Inch - 3/4-16 thread has 16 thread per inch

Metric - M22 x 1.5 the distance between threads is 1.5 mm

3. Determine the thread type: You’ll need to identify whether the thread is tapered (like NPTF) or parallel (like JIC).

NOTE: Thread size is not a direct correlation to the fitting end size. To determine the end size visit our website. View our catalog. 

Step 3: Check the Seal Type

Many hydraulic fittings use O-rings or other seals to ensure a leak-free connection. To measure these seals:

1. Measure the O-ring groove diameter for the fitting. An ORFS Fitting will have the O-Ring groove on the face of the threaded end.  An adjustable stud end will have the O-Ring in a groove within the threads next to a nut and washer, while a non-adjustable stud end will have a groove in the threads next to the hex.  Adjustable and non-adjustable ends are often referred to as ORB, STOR, or O-Ring Port ends.  These diameters can help us determine which O-Ring you may need. 

2. Nitrile (NBR) rubber is the most common compound for hydraulic oil applications.  For other fluids such as fuel or chemical applications, contact Air-Way for guidance on the appropriate compound.

Step 4: Measure the Length and Angle (if applicable)

For certain fittings, the length and  or centerline must also be considered. For example, measurements may be required for the length if it is a straight, or centerline  if its a configuration of 45°, or 90° elbow, tee or cross.

1. Measure the overall length of the fitting if it is a straight fitting.

2. For 90-degree or 45-degree tee or cross fittings, measure the centerline to ensure proper installation.

If there is ever any doubt, feel free to reach out to us, and we can help you identify your needs.

Trust Air-Way for Precision and Reliability

Measuring hydraulic fittings accurately is key to ensuring your system’s performance and safety. By following these simple steps and understanding the specifications of your components, you can confidently select the right fitting for every job. 

With over 70 years of industry expertise, Air-Way is dedicated to providing the highest-quality fittings that meet your precise needs. Explore our comprehensive catalog or contact our team for expert advice on selecting or customizing hydraulic fittings. 

At Air-Way, we’re here to deliver solutions that enhance the performance of your hydraulic systems—ensuring every fitting works seamlessly in your application.