Keg Yield, Pours, and Cost per Ounce
Servings, cost per pour, and pour cost from a keg, computed against the NET yield rather than the number on paper.
Example
You enter
- Keg size half_barrel
- Custom keg volume (gal, 0 to use the preset) 0
- Serving size (oz) 16
- Loss fraction (0-1) 0.15
- Keg cost ($) 150
- Menu price per serving ($) 7
You get
- Gross (oz) 1984
- Net volume after loss 1686 oz
- Servings per keg 105.4
- Cost per serving $1.42
- Pour cost (%) 20.3307
Details, formula, and sources
A half barrel is 15.5 gallons, which is 15.5 x 128 = 1984 fluid ounces, which on paper is 124 sixteen-ounce pints, and nobody gets 124. Foam at the tap, the first pull of a new keg, line cleaning, the heel left in the keg, and the head on every glass take 10% to 20% off the top, and a poorly balanced draft system takes more. Pricing off the gross number is the mistake this calculation exists to prevent. A $150 half barrel poured as 16 oz pints at a 15% loss nets 1984 x 0.85 = 1686 oz, which is 105.4 pints, so the cost is 150 / 105.4 = $1.42 a pint and the pour cost against a $7 menu price is 20.3%. Now tighten the system: cutting the loss from 15% to 8% yields 114.1 pints, drops the cost to $1.31, and moves the pour cost to 18.8%, which is about $11 of margin per keg from balancing the draft lines rather than raising the price. Balancing the draft lines is where that work happens, and pour cost prices a drink once the cost per ounce is known; this calculation produces that cost per ounce. An operating estimate; the bar's own measured yield over several kegs governs.
gross_oz = gallons x 128; net_oz = gross_oz x (1 - loss_fraction); servings = net_oz / serving_oz; cost_per_serving = keg_cost / servings; pour_cost_pct = cost_per_serving / menu_price x 100.
Published US keg volumes (half barrel 15.5 gal, quarter barrel 7.75 gal, sixth barrel 5.16 gal, full barrel 31 gal) and the 128 fluid ounces per US gallon, by name, with a draft-system loss fraction from public bar-operations practice; the bar's own measured yield over several kegs governs.
Keg volumes and the gallon-to-ounce conversion are public. The loss fraction, keg cost, serving size, and menu price are the bar's own values.
Estimate. AHJ and licensed professional govern.
Field names used by the API: keg_size, custom_gallons, serving_oz, loss_fraction, keg_cost, menu_price, gross_oz, net_oz, servings, cost_per_serving, pour_cost_pct
- Keg volumes half barrel 15.5 gal, quarter barrel 7.75 gal, sixth barrel 5.16 gal, full barrel 31 gal; 128 fl oz per gallonUS published keg sizes
- Loss fraction 10% to 20% for a working draft system; higher when the system is out of balancebar operations practice
- Net, not gross pour cost must be computed against net ounces; the gross figure understates the cost of every servingbeverage cost-control practice