O-Ring Size Finder - BS 1806 & Metric Lookup
Verified by Rachel Mayfield, Supply Chain Analyst - April 2026
This O-ring size finder covers BS 1806 standard sizes used across UK engineering. Search by BS number or inside diameter to find the exact size, cross-section, and imperial equivalent. BS 1806 is the British standard for O-ring dimensions, widely used alongside AS 568 (US) and ISO 3601 (metric).
Find Your O-Ring Size
| BS Size | ID (mm) | CS (mm) | ID (inch) | CS (inch) |
|---|
Data from BS 1806 / AS 568 standards. For metric sizes, see ISO 3601-1. Always verify groove dimensions against your seal manufacturer's recommendations.
O-Ring Materials and Selection
O-ring material choice depends on the application's temperature range, chemical exposure, and pressure. The most common materials for UK industrial applications are:
- Nitrile (NBR) - General purpose, -40C to +120C, good oil resistance. Used in 80% of hydraulic applications.
- Viton (FKM) - High temperature, -20C to +200C, excellent chemical resistance. Automotive and aerospace.
- EPDM - Steam and water, -50C to +150C. Not suitable for oils or fuels.
- Silicone (VMQ) - Wide temperature range, -60C to +200C. Food grade available.
- PTFE - Chemical inert, -200C to +260C. Used as back-up rings in high-pressure hydraulics.
Related Standards
- BS 1806 - Dimensions of toroidal sealing rings (O-rings) and their housings
- ISO 3601-1 - Fluid power systems, O-rings, inside diameters and cross-sections (metric)
- AS 568 - Aerospace size standard for O-rings (US/international)
- BS ISO 3601-3 - Quality acceptance criteria for O-rings
References
- BS 1806 - British Standard for O-ring dimensions
- ISO 3601-1:2012 - Metric O-ring dimensions
- Companies House - UK supplier verification
Frequently Asked Questions
What size is a BS010 O-ring?
A BS010 O-ring has an inside diameter of 6.07 mm (0.239 inches) and a cross-section of 1.78 mm (0.070 inches). This is one of the most common sizes in UK hydraulic applications.
What is the difference between BS 1806 and ISO 3601?
BS 1806 uses imperial-derived sizes (AS 568 compatible). ISO 3601 uses metric dimensions. Both are used in the UK. BS 1806 is more common in legacy hydraulic systems, while ISO 3601 is standard for new European designs.
What material should I choose for an O-ring?
Nitrile (NBR) covers 80% of applications - good with oils, fuels, and water from -40C to +120C. Use Viton (FKM) for temperatures above 120C or aggressive chemicals. Use EPDM for steam and hot water. Use silicone for food-grade or extreme cold.
What is the O-Ring Size Finder - BS 1806 & Metric Lookup used for?
The O-Ring Size Finder - BS 1806 & Metric Lookup helps UK engineers find exact sizes, cross-sections, and imperial equivalents of O-rings based on either BS 1806 numbers or inside diameter measurements in millimeters.
Which standards does the O-Ring Size Finder - BS 1806 & Metric Lookup reference?
This size finder references the British standard BS 1806 for O-ring dimensions, alongside AS 568 (US) and ISO 3601 (metric), to ensure compatibility across different engineering standards.
How do I choose the correct O-ring using this lookup tool?
To select the right O-ring size, you can enter either a BS 1806 number or an inside diameter measurement in millimeters into the search field of the O-Ring Size Finder - BS 1806 & Metric Lookup.
Are there different types or variants of O-rings covered by this lookup tool?
The O-Ring Size Finder - BS 1806 & Metric Lookup covers standard sizes and cross-sections for various O-ring materials, including Nitrile (NBR) and Fluorocarbon (FKM), which are commonly used in UK engineering applications.
Where can I find UK suppliers for the O-rings listed in this tool?
For UK-based sourcing of O-rings, you might consider contacting local manufacturers or distributors that stock BS 1806 compliant sizes. Major industrial supply companies like RS Components and MRO Supply often carry a wide range of compatible O-ring materials.
What is the typical cost and availability for O-rings based on this standard?
The cost of an O-ring varies depending on material type and quantity ordered, but typically ranges from £0.10 to several pounds per piece. Availability can be high due to standardized production across many suppliers in the UK.
How frequently is the O-Ring Size Finder - BS 1806 & Metric Lookup updated?
The information provided by Rachel Mayfield as of April 2026 is current, and while updates aren't specified, such tools usually reflect any changes to engineering standards or material advancements when reviewed again.