Keg calculator

A keg holds a fixed volume of beer, but the number of glasses you get from it depends on the size of the glass and on how much beer never reaches one. This calculator starts from the keg sizes the Brewers Association prints, lets you set the serving and a foam and dregs allowance, and turns that into servings per keg, kegs for a party, the time one keg lasts and the CO2 pressure for serving. Please drink responsibly and never drive after drinking; the BAC calculator explains why a rough estimate is not a safe guide.

Keg sizes and what they pour

The first four rows are Figure 1.1 of the Brewers Association's Draught Beer Quality Manual (2019 edition): capacity in gallons and the number of 12-ounce beers, which is the volume in fluid ounces divided by 12 and rounded down. The Cornelius row is our arithmetic from the five gallons the American Homebrewers Association gives, because the manual does not list it. Weights when full, from the same figure, run from 58 lb for a sixth barrel to 161 lb for a half barrel.

How the numbers are worked out

Servings = floor(keg volume in fluid ounces × (1 − allowance) ÷ serving size). Keg volume is gallons × 128. Kegs for a party = round up (guests × servings per guest per hour × hours ÷ servings per keg). Time to empty = servings in the keg ÷ servings poured per hour. Pressure is read from the Brewers Association table of pure-CO2 equilibrium pressure (psig) by beer temperature and CO2 volumes, blending in a straight line between table entries, and adding 1 psig for every 2,000 feet above sea level.

Worked example. A party of 60 guests drinks one 12-ounce serving an hour for 4 hours: 60 × 1 × 4 = 240 servings. A half barrel is 15.5 × 128 = 1,984 fluid ounces; with a 10% allowance 1,786 ounces reach glasses, which is 148 servings of 12 ounces. 240 ÷ 148 = 1.62, so 2 half barrels, with 56 servings to spare. At the party's pace of 60 servings an hour one keg lasts 2 h 28 min. The same party needs 4 quarter barrels or 5 sixth barrels; compare the spare servings in the table to pick.

Limits and common mistakes

The allowance is a guess. The Brewers Association's retailer booklet counts 132 servings from a half barrel poured as 15 ounces of beer in a 16-ounce glass with half an inch of foam, against 124 if each glass held a full 16 ounces. Its manual gives the beer temperature target as 34 to 38 °F, and its carbonation sheet explains that warm beer releases gas and pours foamy, that too little pressure lets the beer foam at first and then go flat, and that beer held too cold over-carbonates.

Pints are not 12-ounce beers. The "165 beers" figure is for 12-ounce servings. A US pint of 16 ounces gives 124. Other glasses differ again, so set the serving to the glass you actually fill.

Size names overlap. A quarter barrel is 7.75 gallons, a sixth barrel 5.16, a Cornelius keg 5 and a Euro keg 13.2, so "half keg" and "keg" mean different volumes in different shops. Check the volume on the keg tag or the brewery's sheet rather than the nickname.

Not all beer is equal alcohol. NIAAA's standard drink is 14 grams of alcohol, so a keg of 5% beer is about 165 standard drinks and a keg of 8% beer about 265. Strong beer calls for smaller pours and fewer servings per guest. The ABV calculator gives a homebrew's strength from its gravity readings.

How many beers are in a keg?

A half-barrel keg, the full-size keg, holds 15.5 gallons, or 1,984 fluid ounces. The Brewers Association's table counts that as 165 beers of 12 ounces, and 124 US pints of 16 ounces. A quarter barrel (7.75 gallons) gives 82 twelve-ounce beers, a sixth barrel (5.16 gallons) gives 55, and a Euro keg (13.2 gallons, about 50 liters) gives 140. Those are plain volume divided by glass size; foam and what is left at the bottom make the real count lower, which is why the calculator takes an allowance you set.

How many kegs do I need for a party?

Multiply guests by the servings each drinks per hour and by the hours, then divide by the servings one keg pours, and round up. For 60 guests having one 12-ounce serving an hour for 4 hours, that is 240 servings. With a 10% allowance a half barrel pours 148, so you need 2 half barrels (56 servings to spare), or 4 quarter barrels, or 5 sixth barrels. The pace of one serving an hour and the 10% are example values, not norms: change them to fit your crowd. Guests drink unevenly, so it pays to keep some spare servings.

How many gallons are in a keg?

A beer barrel is a unit of 31 US gallons (27 CFR 25.11), so a half barrel is 15.5 gallons and a quarter barrel 7.75. The Brewers Association lists a sixth barrel as 5.16 gallons (exactly 31 ÷ 6 would be 5.17), and a Euro keg as 13.2 gallons, which matches the 50-liter keg (50 liters is 13.21 gallons). Homebrewers mostly use five-gallon Cornelius, or "corny", kegs, says the American Homebrewers Association. One US gallon is 231 cubic inches, 128 fluid ounces or 3.785411784 liters.

How much does a full keg weigh?

The Brewers Association manual gives full weights of 161 lb for a half barrel, 87 lb for a quarter barrel, 137 lb for a Euro keg and 58 lb for a sixth barrel. Ice and water for a tub add more.

What pressure and temperature should a keg be served at?

The Brewers Association says most draught systems set their target pressure for beer between 36 and 38 °F, and its manual says the beer should stay between 34 and 38 °F from keg to glass. Pressure follows carbonation and temperature: the table in the Brewers Association's carbonation fact sheet gives 11.3 psig for 2.5 volumes of CO2 at 38 °F and 11.3 psig for 2.6 volumes at 36 °F, at sea level, and adds 1 psig for every 2,000 feet above it (13.3 psig for 2.5 volumes at 38 °F at 4,000 feet). Many lagers and ales fall between 2.3 and 2.8 volumes. Use the pressure mode of the calculator for your beer.

How many standard drinks are in a keg?

NIAAA defines a US standard drink as 14 grams (0.6 fluid ounces) of pure alcohol, which is 12 ounces of 5% beer. A half barrel of 5% beer holds about 165 standard drinks; at 8% the same keg holds about 265. Strong beer turns a keg into fewer, stronger servings; the standard drink calculator counts any glass.

How much beer is lost to foam?

There is no single figure; it depends on the beer temperature, the gas pressure, the draught system and how the beer is poured, all of which the Brewers Association manual covers. The calculator therefore uses an allowance you enter, with 10% as an example. The Brewers Association gives one concrete case in its retailer booklet: a half barrel poured into 16-ounce glasses with half an inch of foam and 15 ounces of beer yields 132 servings, against 124 if every pour were a full 16 ounces. That is a bar's example, not a measured loss rate.

Related: the ABV calculator, the standard drink calculator, the cooking measurement converter for gallons, quarts and fluid ounces, and the recipe scaler for scaling food for the same crowd.

Sources, read October 27, 2026: Brewers Association, Draught Beer Quality Manual (2019), Figure 1.1; Brewers Association, Draught Beer Quality for Retailers (2019), case study I; Brewers Association, Facts About Draught Beer Carbonation (pressure table from the ASBC's Methods of Analysis, 1949); Brewers Association, Performance Guidelines for Refillable Kegs (2017); American Homebrewers Association, An Introduction to Kegging Homebrew; 27 CFR 25.11 (barrel = 31 US gallons); NIST Handbook 44, Appendix C (gallon = 231 in³); NIAAA, What Is A Standard Drink?. How we check our calculators.