Method 1: Estimating malt weight when original gravity is known

Method 2: Estimating malt weight when alcohol by volume and final gravity are known

Method 3: Estimating malt weight from alcohol by volume

Results

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Notes

Cloning (copying) commercial beer recipes takes a bit of guess work because most commercial breweries provide little technical information about their beer. The present calculators were inspired by suggestions from Clonebrews (p. 4 - 5) for inferring the weight of fermentables needed to replicate a commercial beer.

Method 1 relies upon knowing the original gravity. This is the best case situation. These are basic gravity calculations, like gravity points. The following are the formulas from Clonebrews for US units, gallons and pounds.

For method 2, the present calculators use alcohol by volume (ABV) and known final gravity to estimate OG. The formula is from rearranging the ABV formula to solve for OG: OG = (ABV / 131.25) + FG (as specific gravity). The needed fermentables are then determined from the estimated OG like method 1. If the brewery doesn't provide the final gravity, you can use your hydrometer to measure it from a commercial beer sample.

Method 3, an estimate from known ABV alone, was also inspired by Clonebrews. They report alcohol by volume (ABV) divided by constant, such as DME in pounds = ABV / .84. Unfortunately, this constant is not explained or documented. The present calculations estimate original gravity by OG = 1 + (ABV / 131.25) * 1.3, in which 1.3 is a scale-up to estimate the final gravity.

Source

Szamatulski, T. and Szamatulski, M. (1998). Clonebrews: Homebrew recipes for 150 commercial beers. Storey Books, North Adams, Massachusetts.