Grain volume?

Does anyone have a rough idea of how much volume per lb to expect the grain to take up in the mash tun? I've been doing PM so that hasn't been an issue, but I'm moving to all grain and want to know where my limits are for my 5 gallon Igloo (or any other prospective mash tun I may look at). I guess I could fill a pitcher and weight that for a general idea but I assume that there's enough dead space in the grain that "volume of grain" + "volume of water" > "total volume of mash" I tried searching but all I found were threads on how much sparge water to use and how many quarts per lb to mash with.

There are several mash calculators on the web. Here is one. It should tell you how much grain you can fit in your mash tun.

Green Bay Rackers--Mash Calculators

Awesome! That was exactly what I was looking for. Thanks.