Keg Calculator

Worked example

Here is a complete answer with the calculator's default settings, so you can sanity-check the numbers without touching anything — Guests (optional): 50 · Party length (hours): 4 · Keg size: Half barrel (US standard) · Serving size: 12 oz US beer.

Result: 156 12 oz US beers from one half barrel (us standard) · after 5% loss

MEASURE	NOMINAL	AFTER LOSS
Volume	58.67 L	15.5 US gal
12 oz US beer	165	156
16 oz US pint	124	117
UK pint (568 ml)	103	97
Australian schooner (425 ml)	138	131
Australian pot / middy (285 ml)	205	194

Also needed

• Guests drinking beer (40%)20
• Beers needed over 4h100
• Kegs to buy1 keg
• Ice to keep it cold18 kg
• Cups30

Change the inputs above and every figure recalculates.

How the numbers work

Every US keg size derives from one legal definition: a beer barrel is exactly 31 US gallons. A half barrel — the one most people mean by "a keg" — is 15.5 gallons, or 58.67 litres, or 1,984 fluid ounces. Divide by 12 and you get 165 twelve-ounce beers; divide by 16 and you get 124 pints.

Those are nominal figures and no keg ever pours them. Foam, line priming and the sediment at the end cost you beer. A well-tuned system loses about 5%; a professional bar with short lines gets to 3%; a warm day with long lines can hit 10%. So a half barrel realistically pours 110–118 pints, not 124.

Be careful with a figure you will see quoted elsewhere: foam is roughly 25–30% beer by volume. That is the composition of the foam itself, not the share of your keg lost to it. Sites that treat it as a loss rate will tell you a half barrel pours 90 pints, which is badly wrong.

How many kegs do I need for 100 guests?

Use the caterer's rule — two drinks in the first hour, one per hour after — then take the share who actually drink beer. For 100 guests at a 4-hour mixed-bar party that is 500 drinks, of which perhaps 40% are beer, so 200 beers: two half barrels. At a beer-led party where 100% drink beer, you would need four. The calculator does this above.

Is a keg cheaper than cans?

Usually yes, at scale. A half barrel holds about the same as seven cases of 24, and per serving typically works out around 55–65% the cost of cans. The break-even is roughly a 30-guest party. Actual prices swing a lot by state and distributor, so treat the ratio as the guide rather than any dollar figure.

What about UK and Australian kegs?

Both are metric. The UK standard is 50 L, which is about 88 imperial pints at 568 ml each; 30 L gives about 52. Australia also uses 50 L, which pours roughly 118 schooners (425 ml) or 175 pots (285 ml). All are selectable above.