The mark of a good beer is the balance between bitterness and sweetness. A good beer should be neither too sweet nor too bitter. Of course, what makes a good balance is a matter of personal opinion. If you are like most people, you probably prefer a certain type of beer. Your preference may run to very dark beers with a lot of bitterness or sweeter beers with little to no bitterness. Or it may fall somewhere in between.
Beer is naturally sweet. Bitterness is added using flavoring ingredients, such as hops. A good balance has to be achieved or the beer will be either overpoweringly sweet or too bitter to drink. Brewers use a term known as the bitterness ratio to describe the balance in their beers. A bitter beer naturally has a higher bitterness ratio than a sweeter beer. Different styles of beer also have different ratios. An IPA, for example, may have a bitterness ratio that is two or three times as high as a lighter beer.
The bitterness ratio is calculated by dividing the number of International Bitterness Ratio Units (IBUs) in the beer by the number of Original Gravity (OG) points in the beer. Again, the higher the ratio, the more bitter the resulting beer will be.
Home brewers can best learn the fine art of balancing their beers by starting out with a previously crafted recipe for a beer that matches their preferred style. If you are beyond this and want to create your own recipes, you are going to have to do a little math.
Once you design your recipe, you will need to estimate the number of IBUs it will contain. The true number of IBUs for any beer can only really be determined in a laboratory, but home brewers can get a fairly accurate estimate using the following equation: IBUs = U% * (ALPHA% * W* 7489) / (V)
It looks intimidating but U is percentage of hop utilization, alpha varies by the variety of hops you use, W is the weight of the hops you will use in ounces and V is the number of gallons of hops you will use per batch. The utilization factor may vary from batch to batch, depending on how long you boil the hops and several other factors. Your best bet, if you want to get a consistent product, is to try and keep “U” as stable as possible in each batch.
You will need to find your original gravity with a hydrometer, as usual. Once you have your IBU estimate and your OG, you are ready to calculate your bitterness ratio. Take the fractional portion of your OG and multiply it by 1000 and then plug it into this equation: BR = IBUs/OG
For example, if the OG is 1.050 and the number of IBUs is 20, the BR can be calculated as follows: BR = 20/50 = 0.40. This is a very light beer.
What if a light beer is not what you want? One way to increase the bitterness of the beer is to increase the number of IBUs. This can be done by changing any or all of the factors in the IBU equation above. You can use more hops, boil the hops longer or change the variety, among other possibilities. You could also add other bittering agents, such as coriander or ginger. If all else fails, you can change the underlying recipe and use a different grain or different amounts of grain.
Likewise, if the bitterness ratio is too high for your taste, you can lower it by decreasing the number of IBUs. Either use less hops or cook them for a shorter amount of time. You can also add more sweetness and raise the OG.
The math may seem difficult at first, but it becomes easier as you go along, and these formulas are your best bet for getting a perfectly balanced brew.