Rear axle nut size?

My rear wheel bearing (right side) has been whining at me since the snow started to fall. Since the weather here is now pushing the mercury higher up the tube I can finally get this particular fix accomplished. But I don't know what size the axle nut is.
On the site where my parts are "in the cart", they offer sockets from 29-35 mm. A quick search said most are 30 mm but I'm not trusting the google or the AI, I want to know from people who know.

Help me, Obi-Wan, you're my only hope.