Ever wonder how heavy your keg of beer is?
Ever want to figure out approximately how much of your keg was consumed at a party?
Ever wonder what it cost you to supply a party or event (ingredient cost)?
The weight of beer will be the weight of one gallon of water times FG (Final Gravity). The answer is represented in pounds per gallon.
Light Lager with a FG of 1.008: 8.345 x 1.008 = 8.422 lb/g (round to 8.4)
Barley Wine with a FG of 1.030: 8.345 x 1.030 = 8.595 lb/g (round to 8.6)
I took a keg of American Pale Ale to a party and want to know how much of it was consumed and what it cost me. The APA has a FG of 1.015.
Beer weight: 8.345 x 1.015 = 8.470 lb/g (round to 8.5)
The weight of the keg (before going to the party) was 38 pounds. The weight of the keg when I returned home was 13 pounds.
Beer consumed: 38lb - 13lb = 25lb
The weight of my beer that was consumed is 25 pounds.
To find the volume (in gallons) of beer that was consumed divide the weight of the beer consumed by "my" beer weight.
Beer consumed: 25 / 8.5 = 2.94 (round to 2.9) 2.9 gallons of my beer was consumed at the party
The ingredient cost for the party will be the average cost per gallon for my beer ($9.35), multiplied by total weight of consumed beer:
Beer ingredient cost: 9.35 x 2.9 = 27.115 (round to 27.12) My ingredient cost for the party is $27.12
The hydrometer is calibrated to 1.000 for water.
The approximate weight of water is 8.345 pounds per gallon.
The approximate weight of a five gallon keg is 6 pounds but we don't care too much as we are really interested in the product weight.