Friday, 29 October 2021

What is a BU:GU Ratio?

BU refers to bittering units - also known as IBU's (International Bittering Units)

GU refers to gravity units - which refers to how much sugar is in the unfermented wort. This is typically expressed as a figure like 1.050. For the purpose of this ratio, we take all the numbers to the right of the decimal place - so in this example we'd have 50. If the gravity reading was 1.105, then the GU would be 105.

As an example ratio, if a beer had 30 bittering units, and a gravity of 1.030, then the ratio would be 1

Another example would be a beer with 15 bittering units, and a gravity of 1.045. In this case the ratio would be 0.33

Most popular brewing software such as Brewfather will include the BU/GU ratio automatically in your recipe and give you a target bracket based on the style of beer you're making.

In the screenshot below, Brewfather has given us a bracket of 0.57 to 0.95 for the BU/GU ratio - and the recipe is currently at 0.59

This is calculated from 30 BU's and an OG of 1.051 (30/51 = 0.59)

What is BU:GU ratio used for?

The BU/GU ratio is used to balance the levels of bitterness and sweetness within a particular beer. Suggested figures aren't strict rules, but rather guidelines on how to make sure your overall beer flavour remains balanced and suitable to the style you are going for - which is why most beer styles will suggest a range to aim for.

Some example ranges are:
0.25 - 0.35 for wheat beers
0.4 - 0.8 for the majority of ales
1.0 and greater for IPA's

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