[Marquette1997]

I am doing a full volume boil using a partial boil recipe kit...is there a thumb rule for adjusting the bittering hop addition or should I just throw all of the hops in?  Thanks!

[Iliff Ave]

You will get much more extraction thus higher IBUs for a full boil when compared to a partial boil. I would use less but its hard to say how much.

Have you tried to run the recipe through a calculator using both different volume levels to see what the corresponding IBUs would be?

[hubie]

If you want the nitty-gritty, you can read Palmer's section on it here:  http://www.howtobrew.com/section1/chapter5-5.html

It includes a handy nomograph to use for calculations. 

The hop utilization numbers Palmer got from data taken by Tinseth.  If it were me, unless I was going for something very specific in terms of bitterness, I would just toss the hops in and go with the higher IBUs.  If I really wanted to try to correct for it, I would take a rough stab at it by looking up the utilization for the recipe pre-boil gravity and ratio that with the utilization for a full boil gravity.  For instance, say your recipe has you boiling 3 gallons of 1.080 wort for 60 minutes.  From the table that would be a utilization of 0.176.  Now you want to boil 5 gallons for 60 minutes, so your pre-boil gravity is 3/5th 1.080 or 1.048, and your new utilization is about 0.230 or so, so you could cut your hops back to about 0.176/0.230 = 76 percent.

Edit:  I used "efficiency" when I should have used "utilization" to keep the terminology consistent regarding hop usage

[Marquette1997]

Thanks for the ideas...I am brewing this weekend and I think I will try both just throwing them all in and correcting for the full volume...in the end I am sure I will have great brew either way!