An M12 bolt is 12.00 mm (0.472") in diameter. The stocked match is a 1/2" (12.7 mm) inside diameter — 0.7 mm of clearance, the standard substitution for the most common large metric fastener. All sizes ship in seven rubber materials.
Best in-stock matches for M12
| Washer size | Fit |
|---|---|
| 1" OD × 1/2" ID × 1/16" | Compact, general purpose |
| 1-1/4" OD × 1/2" ID × 1/8" | Wider sealing face |
| 1-1/2" OD × 1/2" ID × 1/8" | Fender-style |
| 2" OD × 1/2" ID × 1/8" | Maximum coverage |
Browse every 1/2" ID rubber washer for more OD and thickness options.
Sizing note
M12 fixings usually carry real load — pick an OD at least 2× the bolt diameter so compressed rubber does not extrude out from under the head. 1/8" thickness is the workhorse; step to 3/16" or 1/4" for uneven surfaces.
More metric bolts: M4 · M5 · M6 · M8 · M10 · M16 · M20 — or see the metric conversion guide, Size Finder and size chart.
FAQ
What size rubber washer fits an M12 bolt?
A 1/2" (12.7 mm) inside diameter rubber washer fits a 12 mm M12 bolt with 0.7 mm of clearance — the standard substitution.
Can rubber washers handle structural M12 bolts?
Rubber washers seal and isolate; they are not load-rated hardware. Pair them with a metal washer when the joint carries structural load.