O-Ring Size Chart & Standards Reference
Find the right size across AS568, ISO 3601, JIS B2401, DIN 3771 and metric general standards.
Choosing the correct O-ring size is critical for reliable sealing. Our size chart library covers the five most commonly used international standards, with full cross-reference tables, search-by-dimension tools, and downloadable PDFs for engineering documentation.
AS568
Aerospace Standard 568 (Imperial)
The most widely used imperial O-ring standard in North America. Covers 349 dash numbers from -001 to -475 with inch-based inside diameters and cross-sections.
ISO 3601
ISO 3601-1 (Metric O-Rings)
The global metric standard for O-ring sizes. Organized by inside diameter and cross-section in millimeters. Fully compatible with DIN 3771.
JIS B 2401
Japanese Industrial Standard B 2401
The primary O-ring standard for Japanese machinery and automotive applications. Covers P-series, G-series, S-series and V-series sizes.
DIN 3771
DIN 3771 Metric O-Rings
The German metric standard, functionally aligned with ISO 3601. Widely used in European hydraulic and pneumatic equipment.
BS 4518
British Standard 4518
The established British metric O-ring reference for engineering, maintenance and European procurement teams.
Metric General
General Metric O-Ring Sizes
Non-standard metric sizes commonly used in Asian manufacturing. Available by ID x CS in millimeters with no dash number system.
SMS 1588
Swedish Standard SMS 1588
A Scandinavian sizing reference used in hygienic process equipment, marine systems and Nordic supply chains.
NF T47-501
French Standard NF T47-501
A French metric standard commonly referenced in hydraulic, industrial and automotive sealing applications.
JASO F404
Japanese Automotive Standard JASO F404
An automotive-focused O-ring reference for fuel, oil, coolant and air-conditioning sealing in JDM and global vehicle platforms.
Engineering Tools
Size Converter
Convert between AS568 dash numbers and metric millimeter dimensions instantly.
Open ToolCompression Calculator
Calculate optimal squeeze percentage and gland fill ratio for any size.
Open ToolMaterial Selector
Match your size selection with the right material for temperature and chemical compatibility.
Open ToolFrequently Asked Questions
What is the most common O-ring size standard?
AS568 is the most common standard in North America and globally for inch-based equipment. ISO 3601 is the dominant metric standard in Europe and Asia.
Can I interchange AS568 and ISO 3601 sizes?
Some sizes are dimensionally close but not identical. Always verify the actual ID and CS dimensions before substituting one standard for another. Use our Size Converter tool for exact comparisons.
Do you stock all standard sizes?
We carry the full AS568 range and the most commonly used ISO 3601 and JIS B2401 sizes in NBR, FKM and EPDM from stock. Non-stock sizes are available on 7-15 day lead times.
Can you supply custom non-standard sizes?
Yes. We manufacture custom O-rings to any ID and cross-section dimension. MOQ starts at 1 piece for standard profiles. No tooling is required for cut/vulcanized cord or small-run molding.
Need a Custom Size?
Any ID and cross-section. MOQ starts at 1 piece. Quote within 24 hours.
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