Standard O-Ring Size Chart
Download the O-Ring Size Chart to view standard sizes (O-rings are measured in millimeters).
How to Measure O-Rings
O-Rings are one of the most common types of seals in the world. With an unlimited number of possible manufacturing sizes, they are used various applications across industries. These round mechanical seals keep gas or liquid from passing through an opening but over time, they may wear out and require replacement. If you’re planning to replace an O-ring, a good fit is critical for successful sealing.
Below are the steps to take to properly measure for a new or replacement O-Ring.
- Place the O-ring on a clean, flat, level surface.
- Determine the inside diameter by using a ruler to measure from one inner edge to another.
- Use a ruler to measure the diameter, from one outer corner of the O-ring to the other outer corner.
- Finally, measure the cross-section. Place the O-ring into a vernier caliper. Lightly clamp the jaws of the caliper onto the O-ring, but do not compress it. Record the thickness of the ring (the cross-section, see image for reference).
Frequently Asked Questions
1. How do I determine the correct O-ring size?
Measure the inside diameter (ID), outside diameter (OD), and cross-section of the existing O-ring, then compare those measurements to a standard sizing chart.
2. What if I don’t know my O-ring size?
If you’re unsure, Manufacturer’s Rubber can help identify the correct size using a sample, engineering drawing, or application specifications.
3. Are O-ring sizes standardized?
Yes. Many O-rings follow AS568 standard sizes in the United States, while metric sizes are also commonly used depending on the application and equipment.
4. Why is selecting the correct O-ring size important?
An improperly sized O-ring may leak, wear prematurely, or become damaged during installation. Proper sizing ensures reliable sealing performance and longer service life.
More Resources and Quick Links
- Shop our selection of popular brand O-Rings, like Alfas, Buna, EPR, Viton, and more!
- Check out this post, A Simple Guide to Selection an O-ring for more detailed information.
- Need Parker O-Ring Sizing Gauges? We have those!
- Complete your set up with the Parker O-Ring Installation and Extraction Tools
For more information about O-ring sizes, applications, or orders, contact our team!
