Size reference

O-ring size cross-reference

Enter a dash number, a JIS or BS code, an ID × CS pair or an OXXRING part number. You get the closest size in AS568, BS 1806, JIS B 2401 and metric with the difference in millimetres, and the grades we list at that size.

Public size references, not an official validation of any standard. Nominal dimensions and reference tolerances only. A nearby size is not a substitute — compare the difference against your gland before you change a part.

Try
Unit converter · mm ⇄ inch

Loading size charts…

The two numbers

ID and CS, the only two dimensions we publish

Inside diameter is the hole through the ring. Cross-section is the wall thickness. Every size in these charts is given by those two numbers, so a measurement always refers to the same thing.

How to measure an O-ring

Diagram of an O-ring: inside diameter measured across the hole, cross-section measured through the cord Front view of an O-ring. The ID arrow runs from inner edge to inner edge across the hole. The cross-section view shows the two cut cords; CS is the thickness of one cord. FRONT VIEW ID inside diameterCROSS-SECTION CS CS = thickness of the cord
Reference figure, not to scale.

Cross-reference questions

Cross-referencing a size

Does “same nominal size” mean I can swap the part?

No. It only means the ID and CS of the two sizes are within the reference tolerance of each other. Whether a ring works also depends on the material, the hardness, the groove and the tolerance class on your drawing. Compare before you substitute, or send us the gland dimensions for a review.

Which tolerance does the cross-reference use?

AS568 rows use the tolerance listed for that dash number. BS 1806, JIS and metric rows use a general-purpose tolerance for the size range. When two sizes are compared, the wider of the two tolerances applies. A size is marked close when it is outside that tolerance but within about two and a half times it on ID and twice it on CS. Anything further out is marked different.

What can I type into the box?

You can type an AS568 dash number (214, -214 or AS568-214), a JIS code (P22, G25, S30, V85), a BS 1806 number (BS 207), or a size as ID × CS in millimetres (25 x 3.5) or inches (0.984 x 0.139 in). You can also paste an OXXRING part number. A comma works as the decimal mark.

How do I read an OXXRING part number?

A part number like OXX-OR-24P99-3P53-NBR-70A-P10 contains the size, the material and the hardness. The letter P stands for the decimal point, so 24P99-3P53 means 24.99 × 3.53 mm, followed by NBR 70A. The tool reads the size and shows every grade we list at it.

Why is there no outside diameter?

ID and CS define the ring completely, and they are what you measure and what a groove is designed around. Showing only those two numbers keeps every comparison on the same basis.