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Malt Quantity Calculator
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Malt Amount Calculation Formula
Now that you have all the parts, let’s put them together in the equation we’ll use. Don’t let it intimidate you — it’s easier than it looks once you understand what each term means.
Malt Amount (lbs) = (% Malt Used × Wort Volume × Water Weight per Barrel × Specific Gravity × Plato %) ÷ (% Extract (CGDB) × (1 − % Moisture) × Brewhouse Efficiency)
How the Malt Calculation Formula Works
Brewers use this formula to determine how much malt is needed to reach their target beer specifications — such as volume, strength, and brewhouse efficiency. It’s a practical way to balance the science and art of brewing.
Formula Recap
Malt Amount (lbs) = (% Malt Used × Wort Volume × Water Weight per Barrel × Specific Gravity × Plato %) ÷ (% Extract (CGDB) × (1 − % Moisture) × Brewhouse Efficiency)
By plugging all these values into the formula, you can estimate how much malt you’ll need to hit your brewing targets! Play around with some numbers below.
Calculating Water for Brew Day
In brewing, calculating your total water needs is essential. Since water is lost throughout the process—through grain absorption, evaporation, and equipment—you must work backward from your target fermenter volume.
Example: 10 BBL Batch of American Pale Ale
Target Knockout Volume: 11.0 BBL (into fermenter)
This is the amount of liquid you want to have enter the fermenter at the end of the brew day. We’re talking about a 10 BBL batch, but some beer will be lost in the kettle. If you want 10 BBLs to serve, you should start the fermenter with 11 BBLs.
Kettle Evaporation: 7.6% loss → 0.90 BBL
This is lost to the air while the liquid boils for an hour.
Starting Kettle Volume: 11.90 BBL (after boil losses)
Grain Absorption: 656.9 lbs grain × 0.37 BBL/100 lbs = 2.43 BBL
We’re using 656.9 pounds of grain. When the grain is mashed, some liquid always remains trapped—like a tea bag that stays damp after steeping. A good rule of thumb is that for every 100 pounds of grain, about 0.37 BBLs of water stays absorbed in the grain after the mash.
Mash Evaporation & Equipment Loss: 2% of kettle volume = 0.24 BBL
This amount is lost to the air during mashing.
Total Minimum Water Needed: 11.90 + 2.43 + 0.24 = 14.57 BBL
This is the total amount of water to start with (14.57 BBLs) to make 11.00 BBLs of finished beer.
Splitting Water: Mash & Sparge
When brewing, part of the water is used to mash the grain for about 60 minutes. This allows the enzymes in the malt to break down starches into sugars. After draining the liquid from the grain, some sugar remains trapped. To recover it, the brewer rinses the grain with warm water—a process called lautering.
The total water (14.57 BBLs) is split between mash water and sparge (rinsing) water. The ratio of water used during mashing is important because it affects enzyme performance.
A thick mash (little water) slows down enzyme activity, producing a wort with fewer fermentable sugars—great for malty beers like a Scottish Ale. A thin mash (more water) promotes enzyme activity, producing a drier beer, ideal for styles like an IPA.
Mash ratios typically range from 2 pounds of water per pound of grain (thick) to 4 pounds per pound (thin). For our American Pale Ale, we’ll use a ratio of 3 pounds of water per pound of grain. This should yield a well-balanced wort—fermentable, but not too dry.
We’ll now calculate how much water to mash with and use the remainder to sparge (rinse) the grain.
Calculating Hop Additions (International Bitterness Units)
Repitch Calculator
Many breweries start out using dry yeast cultures for most of their fermentations. Over time, brewers often want more options for flavor and fermentation environment than dry yeast can provide, so they make the move to liquid. With that comes the opportunity to harvest and reuse yeasts across a number of brew days for batch-to-batch consistency and cost savings. Each reuse is called a “generation” and it’s important to track the health and viability of the yeast to determine its useful life.
When reusing generations, there are three stages of yeast management:
- Yeast Cropping: harvesting the yeast from your recently-finished fermentation
- Yeast Storage: creating a healthy environment for the harvest yeast until next use.
- Pitching: adding the stored yeast cells to the next fermentation.
We’ll help you determine the health and viability of your harvested yeast using industry-standard calculations for how much slurry is necessary.