Definition:
AAU's or Alpha Acid Units are a commonly used formulation made famous by Dave Line in The Big Book of Brewing (Amateur Winemaking, Andover, UK, 1974). Though not as accurate as determining IBU's, it provides a very good estimation for home brewers. The formula is found by adding the alpha acid percent per ounce of hops to be boiled for more than 15 minutes, divided by the number of gallons of beer to be made.
