Alcohol

There are two ABV formulas in common use and we ship both, because you should be able to reproduce the number in the book you are reading.

The two formulas

The simple one is the homebrewer’s rule of thumb: the gravity drop times 131.25. It is a straight line, close enough below about 1.070, and steadily more optimistic above that. It is what most recipe books quote.

The one we use by default is the longer expression most software settled on. Its first term is alcohol by weight from the gravity drop, and the second converts weight to volume using the density of ethanol. It diverges from the simple formula above roughly seven percent, and it is the more trustworthy of the two up there. The explanation on the ABV figure shows what the simple formula would have said beside it, because the difference is the honest measure of how much either number is worth.

Which gravities

Both formulas take the original gravity as the beer’s whole sugar, not the reading you took at pitching. If you added sugar to the fermenter, the alcohol comes from all of it, and a hydrometer reading taken before the sugar went in does not know that.

Calories

Calories come from the same pair of gravities by way of real extract, which is the extract still in the beer once the alcohol’s effect on density is taken out. The formula is the standard analytical one, per 12 US fluid ounces because that is how it was published, and we give you 330 mL beside it.

The beer these numbers come from

Reference pale ale — 20 L into the fermenter, a 60 minute boil.

Grist	Amount	Color
Crisp Maris Otter Pale Ale Malt	4.5 kg	2.8 °L
Thomas Fawcett Caramalt	0.35 kg	9.9 °L

Hops	Amount	Alpha	Addition
Magnum	15 g	13.5 %	60 min boil
Cascade	30 g	6.8 %	10 min boil
Citra	40 g	13 %	20 min stand at 80 °C

It comes out at
Original gravity	1.0507
Final gravity	1.0094
Alcohol	5.52 %
Bitterness	35.66 IBU
Color	5.14 SRM (10.12 EBC)
Into the fermenter	20 L

The numbers

Alcohol by volume (abv-cutaia-1995)

5.52 %, from abv-cutaia-1995.

ABV% = (76.08 × (OG − FG) / (1.775 − OG)) × (FG / 0.794)
⇒ Alcohol by volume = 5.52 %

Input	Value	Unit
Original gravity	1.0507	SG
Final gravity	1.0094	SG

What it assumes:

• The other formula gives 5.43 %.

Sources:

• Alcohol by volume from the gravity drop, the “advanced” formula (Zymurgy) — 1995

Alcohol by volume (abv-simple-131.25)

5.43 %, from abv-simple-131.25.

ABV% = (OG − FG) × 131.25
⇒ Alcohol by volume = 5.43 %

Input	Value	Unit
Original gravity	1.0507	SG
Final gravity	1.0094	SG

What it assumes:

• The other formula gives 5.52 %.

Sources:

• How to Brew — John J. Palmer, Brewers Publications, 2017

Calories per 12 US fl oz

165.8 kcal, from abw-real-extract-calories.

kcal/12oz = [6.9 × ABW + 4.0 × (RE − 0.1)] × FG × 3.55
⇒ Calories per 12 US fl oz = 165.8 kcal

Input	Value	Unit
Real extract plato	4.24	°P
Original gravity	1.0507	SG
Final gravity	1.0094	SG

What it assumes:

• 330 mL serving = 154 kcal.

Sources:

• Methods of Analysis — American Society of Brewing Chemists