AAu of hops

[Arbe0]

looking at BYO magazine, it had a recipe that calls for 2.5 AAU Amarillo hops (0.25 oz./7 g at 10% alpha acids) at 60 min.
I am not sure what that all means and how many ounces I should use for a 2.5 or 5 gallon batch.

 

[PZ]

AAUs are the alpha acid percent of the hops times the amount in ounces. In the example provided, 10 AA*0.25 oz=2.5 AAU. If the AA of the hops were 5% the amount you would use would be 2.5/5 = 0.5 ounces. Good luck with the recipe!