Standard O-Ring Size Overview

O-ring size standards define the dimensions and tolerances required for reliable sealing performance. This overview summarizes the most commonly used O-ring size standards, helping engineers and buyers quickly identify the correct sizing system for their application.

Main O-Ring Size Standards

O-rings are generally categorized into inch-based and metric-based sizing systems. Each standard is designed to ensure interchangeability and consistent performance.

• AS568 – Inch-based standard widely used in North America
• ISO 3601 – International metric standard
• DIN 3771 – German / European metric standard

AS568 Inch O-Ring Sizes

AS568 defines inch-sized O-rings identified by dash numbers such as -010, -214, or -325. This standard is commonly applied in hydraulic and pneumatic systems.

View detailed dimensions in our AS568 O-Ring Size Chart.

Metric O-Ring Sizes

Metric O-rings are specified using inner diameter (ID) and cross section (CS in millimeters). They are commonly used in international equipment and European machinery.

• ISO 3601 O-Rings
• DIN 3771 O-Rings

For metric dimensions, refer to the Metric O-Ring Size Chart.

How to Choose the Correct O-Ring Size

• Identify the required standard (inch or metric)
• Measure groove dimensions accurately
• Select appropriate material and hardness
• Verify operating pressure and temperature

O-Ring Groove Design Considerations

Proper groove design is essential to ensure effective sealing and long service life. Groove dimensions must match the selected O-ring size and application conditions.

Learn more in our O-Ring Groove Design Guide.

Standard vs Custom O-Ring Sizes

While standard O-ring sizes cover most applications, custom dimensions may be required for special equipment or unique sealing challenges.

We provide both standard and custom O-rings with OEM support and strict quality control.

Looking for finished products? Visit our AS568 O-Rings and ISO 3601 O-Rings product pages.