What size o-ring would this be?

[Jotel me this]

I have two o-rings, one broke and needs to be replaced. It goes to a small random, older water pipe connector that you cant buy in store so I cant look up a manual . How would someone measure the size of an o-ring for a replacement o-ring? I dont own a caliper and even if I did, wouldnt the o-ring smoosh while being measured, therefore making the measurement inaccurate? Maybe ill have to buy a cheap caliper and measure the port it came off of.

It looks bigger than 3/8th; maybe 7/16th inch? Im trying to avoid buying 1000 different o-ring sizes if possible. Thanks!

 

[gthomas785]

O-rings are sized by ID but there's also thickness and profile that need to match. That one looks like a 5/16 but it's hard to tell for sure from a photo.
If possible, take it into a plumbing supply house and they will match the size.

 

[tlc1976]

It looks like an American size 011. But it could be a metric size. Or even proprietary size. Also depends what it’s going into, as to how much room there is to crush it before something breaks.

If you don’t have a knowledgeable plumbing supply store, an auto parts store is another good option.

 

[mcdougy]

There are packs at HD in the plumbing parts for aprox. 2 dollars with random sizes if your not confident you know the exact one.