How to measure an O-Ring?
O-rings are actually really easy to measure. All you need to do is measure the internal diameter (ID) or outside diameter (OD) and the width or cross section (C/S) of the o ring. The diagram shows exactly where these dimensions are to be found. Once you have these measurements you then need to decide if the size you need is listed below or if the best fit will be a metric oring. Once you have the AS-568 dash size you need, select the compound link at the bottom of the page to place your order.
To calculate an o-ring's outside diameter (OD) you may use this formula: 2(CS) + ID = OD
If you have the OD and need to find the ID use this formula: OD - 2(CS) = ID
