How to Measure a Rubber Washer
Finding the right replacement rubber washer starts with three measurements: outer diameter (OD), inner diameter (ID), and thickness. Here's exactly how to measure each one.
What You'll Need
- A caliper (digital or vernier) for accurate measurements
- Or a ruler for approximate measurements
- The washer you need to replace (if available)
Step 1 — Measure the Outer Diameter (OD)
The outer diameter is the total width of the washer from one outside edge to the other. Place your caliper across the widest point of the washer. This is your OD measurement.
Step 2 — Measure the Inner Diameter (ID)
The inner diameter is the size of the hole in the center of the washer. Insert your caliper into the hole and measure across. This is your ID measurement — it should match or slightly exceed the bolt or fitting diameter it will sit on.
Step 3 — Measure the Thickness
Lay the washer flat and measure its height with your caliper. This is the thickness. Thickness affects how much compression and sealing force the washer provides.
Tips for Finding the Right Size
- If your washer is worn or compressed, measure the bolt/fitting ID instead and add 1/16" to 1/8" for the washer ID
- OD should be large enough to cover the surface area you need to seal or protect
- When in doubt, go slightly larger on OD and slightly smaller on ID for a better seal
- All our washers are listed by OD x ID x Thickness — e.g., 3/4" OD x 3/8" ID x 1/16" Thick