10 Gal mash tun

I use a 10 Gallon Rubbermaid for my mash tun. I was wondering if anyone has an idea of how much grain it will hold? I know it depends on the mash water ratio. I’m thinking about brewing an imperial stout that uses 22-23 lbs of grain.

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26 Lbs at 1.2qt/Lb is the most I can fit in mine.

I use the same cooler for my mashtun and I’ve decided after a couple of big beers that that I’m not going to go north of ~18 pounds of grain in it. I like a thinner mash to be able to stir and for anything bigger than that I’m just going to cheat it out with some DME additions. No shame in that. Plus, I get much poorer efficiency the further I fill that thing up so with the DME I can take a gravity reading during the boil and determine how much I need to add at that point to hit my target goal.
This method isn’t for everyone, but it’s easier for me so I’m rolling with it.

OK, thanks for the info. I may wait until I get and convert a big ass cooler for imperials.