BU:GU Ratio

After reading the book "Designing Great Beers" by Ray Daniels, I've become accustomed to using one of his terms that he introduces called the BU:GU Ratio.  The ratio is a rough calculation, but a quick way to determine how the beer is going to taste before you even taste it (or buy it), and plus, if you drink a lot of craft brews you can impress your friends, so let me lay some knowledge on you.

The BU stands for Bitterness Units.  This is essentially the same number as the IBUs (or International Bitterness Units) of the beer, which most craft breweries print right on the label.  From a homebrewing standpoint, in order have IBUs of a beer you must boil hops.  Any additions of hops after the typical 60min boil result in IBU=0, so boiling them is crucial to beer making.  Most people assume that the IBU number tells you how bitter a beer will taste, but that's not very accurate at all.  The bitterness flavor is also in competition with the malt flavor of the beer, which we learn from the GUs.

The GU stands for Gravity Units.  This number is slightly more difficult to find on labels and if they do print it on the label, they'll print it as the OG, which stands for Original Gravity.  The OG tells us the original concentration of the sugar (in kilograms per liter) just before the yeast is pitched, and it typically looks like this: OG=1.050, which means the original gravity of the beer is 1.050 kg/L.  To convert OG to GU you simply take the non-zero digits from after the decimal.  For example, if OG=1.048 ---> GU=48.  Since the GUs stem from how much sugars we extract from the grains, it gives us a good estimate of how malty a beer will taste.

Now comes the easy part, we simply divide the BU by the GU and we get the BU:GU ratio, which typical values fall between 0.20 and 1.20.  The lower this value, the more malty your beer will taste, and the higher the value, the more bitter it will taste.  I've heard that a nice balance between malty and bitter is with a BU:GU ratio close to 0.50, but it really is a preference to the beer taster, so I'd recommend trying certain beers that you like and make note of the BU:GU ratio.  If the company doesn't print the OG or IBU on the label, you can probably look it up on the brewing company's website, or if that doesn't work, typing the beers name in a search engine works as well.  Trust me, someone will know these values.

Let's do a quick example, a barley wine that has an OG=1.115 and IBU=70:
BU=70
GU=115
BU/GU = 70/115 = 0.61
This tells me it'll have a fairly balanced taste slightly leaning towards a more malty flavor.

Keep in mind, this is nothing but a ratio for individual use, it doesn't really have a definite line separating malt from bitter tastes, so largely it depends on you.  Obviously, there are extreme beers that you'd be crazy not to think tasted like malt or tasted very bitter, but the ratios in between are very subjective.  So have fun with it and use it whenever you can.  Maybe you'll find that no matter what the style of beer you drink you prefer a narrow range of BU:GU ratios.

Source:  "Designing Great Beers" by Ray Daniels