Mash Tun Volume Question

[RLinNH]

I upped my Boil kettle to a 30 gallon Blichman. I have already used it once on an Ordinary Bitter. Worked out well on such a low O.G. beer. Here's the issue. I am now planning on brewing my house beer. I have a 20 gallon Mash Tun. I will be placing 45lbs of grain into that tun, then adding 15 gallons of water to that to get my mash temp. I feel that I will have an issue there, but, I would love to bring my mash out temp to 168 degrees after that. Do any math guys out their have a formula that would make me more at ease as far as doing this brew day? Worse comes to worse, I will sparge into 5 gallon buckets, then dump those into my boil kettle. But I have a feeling that I will be needing a 30 gallon Mash Tun. Something I did not pay attention to when I upped my Boil kettle... Thoughts?

On Deck- Maibock Helles

 

[jbaysurfer]

Here ya go. 3rd calculator down "Can I Mash It?"

http://www.rackers.org/calcs.shtml

 

[jbaysurfer]

Edit for simplicity, use the rest calculator on the same page and see that you'll likely need in the neighborhood of 26Qs of Boiling water for that infusion, and 17.6G of space for the initial mash in. No, 20Gs isn't enough for both. Batching into buckets works fine, I've done it a bunch.