How to Calculate Brewhouse Efficiency

Brewhouse efficiency is an important concept to understand. The efficiency of an individual’s brewing practices and system is ultimately responsible for their original gravity and how much grain will be required to brew a given recipe.

What is Brewhouse Efficiency?

Brewhouse efficiency is a measurement of potential fermentables converted into sugar in your wort. It takes into account different losses for your specific brewing practices and setup, including; mashing, lautering, hop trub, and transfers (boiling creates insignificant losses). This is a cumulative measurement of these losses taken right before the yeast is cast and fermentation begins.

Individual efficiency at these “loss points” can be measured to get some idea of how efficient a given brewing practice is. You can take a specific gravity reading at different points in the mash (mash efficiency), as you sparge (runoff efficiency), before the boil (pre-boil efficiency), etc.; and compare these numbers to both the recipe’s maximum potential yield (we will go over how to calculate this) and your overall brewing efficiency.

This will give you some idea how much you are losing at each point, what step is responsible for the highest loses, and areas where you may want to try for better efficiency. This is an interesting experiment to do a couple times, but in the end, it is the brewhouse efficiency that you will be using most interested in.

Once you know your typical brewhouse efficiency—an average taken from brewing several different recipes exactly as written—you can then use it to create your own recipes and adjust the grain bills of borrowed recipes to best fit your system.

The Efficiency Hidden Within Your Grain Bill

Each different malt in an all-grain recipe has an extract potential. This potential is a measurement of how much sugar per pound of said malt can contribute to your beer.

To calculate this potential go to the malt manufacturers website and pull up a data sheet on the malt you are looking at using. Find the Extract DBFG (Dry Basis Fine Grind), which may sometimes be displayed as “Extract %,” but be sure you are not confusing it with the DBCG (Dry Basis Course Grind). The DBFG is the malt’s maximum extract or fermentable sugar yield as found in a laboratory setting.

It can be thought of as the malts maximum extract potential and a potential unattainable for any brewer, even the large commercial ones. But this number can be used, with some calculating, to find an entire recipe’s maximum potential, which you then can use to measure your own system’s brewing efficiency.

Calculating Grain Points

Sucrose (pure sugar) is used as the standard measurement of reference because it would yield 100% soluble extract in a liquid. The specific gravity of one pound of sucrose in one gallon of water is 1.046. To make these calculations a little easier we can turn any specific gravity into what’s sometimes called grain points, by subtracting 1 and multiplying by 1000.

So, the base reference number for sucrose is 46… and is the number we will measure all our malts against.

Now, you can take the DBFG of any malt and multiply it by 46 to get that specific malt’s “grain points”. For example, let’s take this pale ale malt. As you can see on the page, the DBFG is 81.5% — written here as Extract (dry).

So, to calculate the grain points for the pale ale malt we turn the 81.5% to decimal form and:

Rounded to the nearest whole number gives us 37.

Calculating Maximum Yield For a Recipe

Our next step would be to do this for an entire recipe. As an example I’m going to use Ben Stange’s brown ale recipe from his Spicing Up Your Holidays article.

The malt list consists of; 2 Row malt, 90 L Crystal malt, 60 L Crystal malt, Chocolate malt, and Black Patent malt. Don’t worry about the amounts yet, we’ll get to that in a minute. Right now let’s just calculate grain points for each.

I’m using Briess Malting Company as a reference for all these malts except the chocolate and black patent. Because these darker malts contribute little to the potential yield and are used only as color and flavor enhancers the Briess data sheets don’t list their DFBG.

If you find yourself in this situation, there’s a couple good references that do list an average of the data you need. BeerSmith lists potential SG, so drop the 1.0 and you have your grain points. Also, the “Malted Grain” chapter on John Palmer’s “How to Brew” site, lists Max PPG (points/pounds/gallon) which is the same as your grain points. You’ll notice this one is very general.

These references are great but, whenever possible, it is more accurate to get them straight from the specific manufacturer’s data.

Grain Points:

• 2 Row = DFGB of 80.5%
• 90L Crystal (caramel) malt = DFGB of 75%
• 60L Crystal (caramel) malt = DFGB of 76%
• Chocolate malt = Potential SG 1.028
• Black Patent = Potential SG 1.025

So, drop the 1.0 on the chocolate and black patent and we have our grain points for those. Let’s get the points for the first three. Using 46 (sucrose reference number) as our standard, we calculate:

Total Potential Points:

Next, we use the following formula to calculate the total potential for each grain, in accordance to this specific recipe and batch size:

Applying this to our Brown Ale recipe:

Important Note: There are 16 ounces in a pound, so to change ounces to pounds you simply divide the number of ounces by 16. You may notice that I’ve done this calculation for the Chocolate and Black Patent above.

Adding up Potential Yield:

If we then add these all together we get a maximum potential yield for this batch of beer.

Another Important Note: If a recipe has adjuncts don’t forget to take these into account when calculating the recipe’s maximum potential yield (total grain points). Both references listed above have average numbers for most adjuncts you are likely to use.

Calculating a Recipe’s Brewing Efficiency

With a maximum potential yield of 83 (Original Gravity of 1.083) we can then calculate what Ben was looking at for his brewhouse efficiency.

He has an original gravity of 1.058 for our example recipe. We can take this, compare it to the maximum potential yield, and come out with an overall brewhouse efficiency:

So, a brewhouse efficiency of 70%, which falls right in line with most homebrewing efficiency numbers, which are usually between 65 and 80 percent.

From now on, if brewing efficiency is not given to you in a recipe, you can do these same calculations and figure it out for yourself.

Your Brewing Efficiency

Remember, doing the above only calculates what the recipe’s creator had designated the brewing efficiency to be. This may not be your system’s efficiency. To figure out yours, you have to brew that recipe on your system and see what kind of original gravity you come up with. Then you can figure out your own efficiency the same way.

For instance, let’s say you brew our example Brown Ale recipe exactly how it’s written and come up with an original gravity of 1.062.

Good on ya! Your practices and system lend a little more efficiency. This means you could actually brew this recipe with slightly lower amounts of malt.

Or, it could go the other way. Say you got an original gravity of 1.050.

In this case your efficiency is lower than it really should be and you need to look at changing your practices or setup to increase it. Remember, on average, homebrew brewhouse efficiencies fall somewhere between 65% and 80%, with most falling in the comfortable mid-70’s. But even if you don’t make any changes to your practices or setup, you can now brew this recipe and come out close to the target original gravity.

Increasing Efficiency:

With an efficiency of 60% you can calculate the additional grain needed to hit 1.058. You can do this by, taking the target original gravity (1.058) and dividing it by your brewing efficiency (60). Like so:

So, you know you need 97 total potential grain points to hit 1.058 original gravity at 60% brewhouse efficiency. Then you have to decide how you are going to divide those extra 14 points into the grain bill. The easiest way to do this is to get the points out of your base malt. In this case that would be the 2-row. So, we play with the math:

As you can see, the math is telling us that each pound of 2-row is worth 7.4 grain points. Knowing this, we now figure out how much we need to add:

This would be account for the approximate amount that we need added. This gives us a total 98 grain points, which will then increase your brewhouse efficiency within our target range… And there you go, you’re off and running.

Adding Adjuncts

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Of course you’re saying, “Ok, that’s great for next time, but what do I do with this beer I just brewed?” This immediate problem—having a beer at a lower gravity than expected—can be simply ignored and allowed to ferment out to a slightly lower alcohol, but still pleasant brew; or you can add adjunct sugars.

An adjunct is usually defined as any source of starch that is not malted, though many brewers will put things like malted wheat and rye in this category too. They can be further broken into two categories; kettle adjuncts and mashable adjuncts.

For our situation, we are only interested in kettle adjuncts. Kettle adjuncts are sugars that are readily fermentable. They include honey, candi sugar, molasses, any variety granulized sugar, malt syrup, malt extract, etc. Many of these can be added directly to the fermentation vessel, though putting them, first, in some heated water will help them solubilize. I have added honey straight to the fermenter on several occasions to up the original gravity. The important thing to consider is how the flavors of any adjuncts will fit into the profile of the style you are brewing.

Adding adjuncts becomes especially relevant if you happen to miss your target volume. If, after the boil, you find you have 4.5 gallons (instead of the target 5 gallons) at a gravity of 1.058 what do you do? Well, first don’t fret. You have two choices, neither of which includes throwing the beer out.

First, you could accept the smaller volume. If you do this there is an extra step to figuring out your brewing efficiency because the differing volumes need to be taken into account. So the calculation becomes:

Using the above formula, let’s say you got a reading of 1.058, but only had 4.5 gallons collected.

Second, you could add water until you have the targeted 5 gallons. In this case take a gravity reading after you add the extra water, but before you add any adjunct sugar (if you are going to), and figure the efficiency as first described, by dividing the measured points by the potential points. Then add your adjuncts to bring the gravity up to the target original gravity of 1.058, or whatever it happens to be.

After making these calculations several times you can come up with an overall average brewhouse efficiency. Do this by adding several trial brew house efficiencies together and then dividing by the number of trials. Like so:

Let’s say you did the calculations five times, and get 70%, 68%, 71%, 69%, and 70%, respectively.

And remember the more trials the higher the accuracy.

That’s It.

Well there it is… brewhouse efficiency. Hopefully this helps you calculate your own average brewhouse efficiency, what efficiency a given recipe was built around, and if you need more or less grain for a recipe. And having your individual brewhouse efficiency figured will let you know when your brewing equipment or practices might need some adjustments and becomes a vital piece of the puzzle when you start to design recipes.

Cheers!