IBUs, or "International Bittering Units" is the number breweries use to indicate the bitterness of the beer you are drinking. But what is it? Why does it matter? Can you use it? click through to find out.
So I see IBU 40 on my beer, what does that mean?
Well let's take a step back and talk about hops. Hops are the reason in the brewing process that gives beer it's bitterness, those wonderful little flowery pieces of nature that give us that great part of the beer flavor. When beer being brewed hops need to be added as a necessary portion of the brewing process, but how much get added you ask? that depends on what type of beer you are trying to brew. The more hops you add the bitterer your beer will be.
Hops add what are know as isomerized alpha acids, that's the bitter taste you get, and according to the IBU Wikipedia page a Bittering Unit is "1 milligram of isomerized alpha acid per liter" or for you math whizzes out there it's literally on part per million. if you want to calculate you own IBU there's a handy formula located on the Wiki, as well as good article on byo.com.
That's some pretty potent stuff, and more more you have the bitterer you get. IPAs for example will be around 40 to 60 IBUs. An interesting note from the articles is that the more malt that is used to brew a beer the higher an IBU rating will have to be to get that bitterness across. Malts apparently are the base to the hops acidity and balance the flavor, so a beer with a higher malt content will tend to have a higher IBU rating. So you might have a Stout or Porter for example could have a higher IBU rating than an IPA, but you wouldn't know it by tasting it.
So that's an IBU for you in a nut shell. It ends up being an excellent way to navigate inside of a taste profile that you enjoy. There are a number of scales around telling you the approximate IBU rating you can expect from each type of beer which should give you a jumping off point to try something new. A short list I found here, and can give you an idea of what your shooting for if that hops flavor is what you like.