here are three main measurements that matter when specifying rubber tubing dimensions– inner diameter (ID), outer diameter (OD), and wall thickness (WT). When you are ordering or requesting a rubber tube to be manufactured, you will need to know at least two out of the three dimensions. The combination of measurements will vary based on your specific application requirements and acceptable tolerance ranges.
The image below depicts each measurement of a tube.
If you only know two of the dimensions, you can easily calculate the remaining dimension with one of the formulas below.
O.D. = I.D. + 2(W.T.)
I.D. = O.D. – 2(W.T.)
W.T. = (O.D. – I.D.) / 2
If you are physically taking any of these measurements, you should try to avoid causing any deformation during measurement, especially if it’s a lower durometer rubber that is soft and pliable. Depending on the size of the tube, there are a few different measurement tools that can be used, like calipers or pin gauges, to get accurate measurements. You should also factor tolerances into your size specifications and confirm with the manufacturer that these tolerances can be held.