Mash tun size for 3gal and 1 gal

[juskojj]

I only want to brew 3gal and 1 gallon all grain. I like hefe-weisse and stouts, along with Belgium style. Can I get by with a 5 gallon cooler or so I need larger?

 

[MMX]

This is a handy tool. Scroll down to the "Can I Mash It?" calculator.