Measure the inside diameter (ID) and cross section (CS) first. That is the fastest way to match the right size, shop small packs, or send a useful quote request.
The distance across the center opening of the O-Ring. Record this first when you measure.
The thickness of the O-Ring body. A small change here matters, so measure carefully.
Useful for checking the ring, but not the best way to search or buy. Use ID + CS when possible.
Enter any two values in millimeters. Use ID + CS to calculate OD, or OD + CS to reverse the ID before you search or request a quote.
This page is meant for real customers, not engineers only. Keep it mm-first, record both values, then move to exact size shopping or quote.
Place the caliper jaws inside the ring and measure across the widest inner opening. Record the reading in millimeters.
Measure the ring thickness itself. This value changes the fit quickly, so double check and avoid estimating.
OD helps confirm the ring, but it is usually a secondary check. To find the right product, start with ID + CS.
OD = ID + (2 x CS)
Example: 25.20 + (2 x 3.53) = 32.26 mm
Move straight into exact-size small packs, or switch to quote if you need 100+ pcs or a custom size.
Start with ID and CS. OD is useful for checking, but ID + CS is the cleaner path for finding a match and buying the right ring.
Use the best ruler you have, take multiple readings, and upload a photo or sketch through Bulk Quote if you want a second check before ordering.
Millimeters first. You can convert inch values if needed, but mm keeps the buying logic cleaner and easier to match.
Yes. Send any measurements, photos, or drawings you have. That is especially useful when you are not fully sure about the exact ID and CS.
