Adjusting Recipes: Volumes, Efficiency, Extract

With nearly 100 homebrew recipes posted on The Mad Fermentationist over the last four years it was time to post a guide on how to adjust them for different setups.  I post the recipes as they were brewed with the actual volume and efficiency rather than converting them to a consistent format, and I realize that this can be a hassle.  Whether you want to brew a batch that is a different volume, your efficiency is different than the recipe, or you brew with extract, this guide will show you how to adjust the recipes to suit your system.

Many of these calculations are easy to do with a copy of BeerSmith, ProMash, BeerAlchemy, or one of the dozens of other programs/websites/spreadsheets designed to do recipe calculations.  However, I think it's important to develop some instincts on how recipe adjustment works.  Fairly frequently I hear someone complain that they accidentally doubled the hops (for example) and didn't realize until it was too late (and the wort was in the fermenter).

Volume
To convert a recipe to a different volume multiply each of the ingredient (hops, malt, sugars, spices, fruit etc...) by the size of your batch divided by the size of the recipe.  For example: if the recipe is designed to produce 5 gallons of wort and you want to brew 10, multiply the weight of each of the malts (adjuncts, sugars, spices, fruit) by 10/5 = 2.

For the hop additions rather than doubling the weight of each addition double the amount of alpha acids contributed by each addition.  To do this take the weight of each hop addition in the recipe and multiply it by the percent alpha acids called for and the ratio of the batch sizes, then divide by the percent of alpha acids in the hops you are using. If a 5 gallon recipe calls for 1 oz of 5% AA hops and you want to brew 10 gallons with a 4% AA hop the formula would be: (1 oz * 5% AA * 10/5)/4% AA = 2.5 oz of 4% AA hops.  The same formula can be used to adjust a recipe for lower/higher AA% hops in the same size batch.

Here is an example of scaling a recipe from a four gallon batch to a five gallon batch.  Let's assume that the Magnum hops are 12% AA and the Saaz are 4% AA.

German Bitter

Recipe Specifics
----------------
Batch Size (Gal): 4.00 to 5.00
Anticipated OG: 1.044
Brewhouse Efficiency: 70 %
Wort Boil Time: 80 Minutes

Grain
------
69.2% - 4.50 lbs. French Pils (4.5 lbs * 5/4 = 5.6 lbs French Pils)
15.4% - 1.00 lbs. German Wheat Malt (1 lbs * 5/4 = 1.25 lbs German Wheat Malt)
15.4% - 1.00 lbs. German Munich (1 lbs * 5/4 = 1.25 lbs German Munich)

Hops
------
0.38 oz. Magnum (Whole 14.50% AA) @ 75 min. ((.38 oz * 14.5% AA * 5/4)/12% AA) = .57 oz of 12% AA Magnum
1.00 oz. Czech Saaz (Whole 3.30% AA) @ 5 min. ((1 oz * 3.3% AA * 5/4)/4% AA) = 1 oz of 4% AA Czech Saaz

Extras
-------
0.50 Wirlfloc @ 15 min. * 5/4 = .628 Whirlfloc
(For finings I usually wouldn't bother with this conversion for a small change in volume.)

Yeast
------
WYeast 2565 Kolsch (5/4 =1.25 times more yeast)

Mash Schedule
----------------
Sacch Rest - 90 min @ 148 (no changes, except to use more mash/sparge water to hit your desired pre-boil volume, which in turn depends on your boil-off rate.)

Efficiency
To adjust a recipes for your efficiency multiply all of the grains/malts by the efficiency listed in the recipe divided by your expected efficiency.  You only need to adjust the ingredients in the mash, no changes to other fermentables (such as sugars or fruit) or other recipe parameters such as hops, yeast, or finings.  Some sources recommend only scaling the base malt to adjust for efficiency, but if you are extracting fewer sugars from the mash you are also extracting less flavor/dextrins from the specialty malts.

Let's look at a recipe that calls for 10 lbs of pale malt and 1 lb of crystal 80 with 70% efficiency.  If you are expecting 75% efficiency you'd multiply each of the malts by .70/.75 = .933.  So you'd use 10*.933= 9.33 lbs of pale malt and 1*.933=.93 lbs of crystal 80.

Here is an example of converting the five gallon recipe above from 70% to 80% efficiency.

German Bitter

Recipe Specifics
----------------
Batch Size (Gal): 5.00
Anticipated OG: 1.044
Brewhouse Efficiency: 70% to 80 %
Wort Boil Time: 80 Minutes

Grain
------
69.2% - 5.60 lbs. French Pils  (5.6 X .70/.80 = 4.9 lbs French Pils)
15.4% - 1.25 lbs. German Wheat Malt (1.25 X .70/.80 = 1.1 lbs German Wheat Malt)
15.4% - 1.25 lbs. German Munich (1.25 X .70/.80 = 1.1 lbs German Munich)

Hops (no changes)
------
0.57 oz. Magnum (Whole 14.50% AA) @ 75 min.
1.00 oz. Czech Saaz (Whole 3.30% AA) @ 5 min.

Extras (no changes)
-------
0.63 Wirlfloc @ 15 min.

Yeast (no changes)
------
WYeast 2565 Kolsch

Mash Schedule
----------------
Sacch Rest - 90 min @ 148 (slightly less mash and sparge water will be needed to hit your pre-boil volume to account for less absorption by the grain.)

Extract
If you brew relying on malt extract for the bulk of your fermentables you can still make most of the recipes I've posted.

To determine the amount of liquid malt extract to use multiply the amount of each base malt by the efficiency of the recipe, if using dry malt extract multiply that number by .84 (this accounts for the more concentrated sugars in DME compared to LME).  Make sure to pick an appropriate malt extract(s) (pils, English pale, pale/light, smoked, and/or Munich) to replace the base malt called for by the recipe.

Remember that wheat and Munich extracts will replace both the wheat malt or Munich as well as some of the pils/pale in the recipe.  In general I recommend against using darker extracts as they tend to be less fermentable, and it is hard to know the proportions of the malts used (or with some manufacturers even what those malts are).

Any caramel (including Special B), crystal, roasted malts/grain (roasted barley, Carafa, chocolate, pale chocolate etc...) can be crushed and steeped in the amount listed by the recipe without adjustment. 

If you are doing a full boil there is not need to adjust the hop additions.  If you are doing a partial boil the only hop issue of great concern is that IBUs saturate the wort around 100.  So if you end the boil with 2.5 gallons of wort the most bitterness you can have when you dilute the beer to 5 gallons is 50 IBUs (100*2.5/5 = 50).  For a long time it was assumed that there was lower hop utilization as the gravity increased, but from what I have read recently this is not the case (namely John Palmer's about face on the issue).

German Bitter (5 gallons Extract)

Recipe Specifics
----------------
Batch Size (Gal): 5.00
Anticipated OG: 1.044
Brewhouse Efficiency: 80 %
Wort Boil Time: 80 Minutes

Grain
------
I would look at the wheat first since it will contribute to both the wheat and pils.

15.4% - 1.1 lbs. German Wheat Malt
We'll imagine our wheat DME is 50% wheat and 50% pils.  So 1.1 (weight of the grain) / .50 (percent of wheat in the extract) * .8 (efficiency of the original recipe) * .83 (DME conversion factor) = 2 lbs wheat DME

69.2% - 4.9 lbs. French Pils
Since the wheat extract was 50% pils we can subtract the equivalent of 1.1 lbs that it already added, leaving us with 4.9-1.1 = 3.8 lbs.  Using pils DME 3.8 (weight of the grain)  * .8 (efficiency of the original recipe) * .83 (DME conversion factor) = 2.5 lbs of pilsner DME

15.4% - 1.1 lbs. German Munich Malt
Using 100% Munich LME 1.1 (weight of the grain) * .8 (efficiency of the recipe) = .9 lbs Munich LME

In this case there are no grains that need to be steeped, and there is nothing wrong with that.

Hops
------
0.57 oz. Magnum (Whole 14.50% AA) @ 75 min.
1.00 oz. Czech Saaz (Whole 3.30% AA) @ 5 min.

Extras
-------
0.63 Wirlfloc @ 15 min.

Yeast
------
WYeast 2565 Kolsch

Mash Schedule
----------------
Sacch Rest - 90 min @ 148

There are some limits to extract with steeping grains. Many specialty malts like Victory, biscuit, amber, brown, melanoidin, as well as unmalted adjuncts (corn, wheat, rice, rye, and oats) need to mashed with an enzymatic base malt to convert their starches to sugars.  Malted grains like rye, wheat, and oats have enough amylase enzyme to self-convert. Partial mashes are relatively easy to accomplish without any special equipment.  In fact partial mashes are just like steeping except that you have to put a bit of extra effort into using the right ratio of grain to water (between 1 quart per pound and 2 quarts per pound) and holding the right temperature (~150 F) for at least 30 minutes.

To convert an all-grain recipe to partial mash simply use as much grain as you want (making sure there are two pounds of enzymatic malt for every one pound of something else) and then use the method above to convert the remainder of the base malt to extract.  You may need to add more extract depending on the efficiency of your partial mash (if you are lazy or don't know your efficiency you can keep extra DME on hand and add more to adjust as needed).  Once your mash is complete remove the grains and add the extract and any additional water, continuing with the rest of the recipe as instructed.

Summary
If you need to make more than one of these adjustments the order doesn't matter, so you can adjust for volume and then efficiency or t'other way round.  Hopefully this little tutorial will help give you an idea on how to convert and adjust recipes for your system.  If anything wasn't clear, or if I missed your particular situation please send me an email at madfermentationist@gmail.com and I'd be happy to update this.

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