Keg Servings Calculator
Keg size and pour to servings minus foam.
What it does
Keg math decides whether the party runs dry at ten or pours past midnight. Volume divided by pour size, minus foam, gives servings. A half barrel stretches past 150 twelve-ounce pours when the system behaves.
The tool above takes keg size, pour, and foam share in imperial or metric and prints whole servings plus foam loss. US kegs run in barrel fractions; metric kegs run 50, 30, and 20 liters with milliliter pours.
Federal barrel volumes anchor US keg sizes through TTB standards while brewers associations publish the serving arithmetic both systems use. Foam near 5 % marks a balanced rig; double digits mean warm beer, fast pours, or pressure trouble.
Buy by heads times drinks divided by servings, round up, and keep a spare sixth for the toast. Chill a full day to 38 F, check IDs, and plan rides before tapping.
How to use
- Pick imperial (gal, oz) or metric (L, mL).
- Pick the keg size from the list.
- Enter pour size.
- Set foam loss percent.
- Read servings and foam loss.
- Chill, balance, and pour patiently.
Formula
- keg
- Keg volume in gal (L metric).
- pour
- Pour size in oz (mL metric).
- foam %
- Share lost to foam and waste.
Volume uses gallons times 128 ounces (or liters times 1000 mL) with servings floored to whole pours. Foam share defaults 5 % for a balanced system; wild pours run 10 % or more.
Worked example
Example: half barrel, 12 oz pours
Half barrel, 12 oz pours, 5 % foam loss.
- Half barrel is 15.5 gal = 1984 oz.
- Foam loss 5 %: 1984 x 0.05 = 99 oz.
- Good beer: 1984 - 99 = 1885 oz.
- Servings at 12 oz: 1885 / 12 = 157.
- Chill to 38 F and pour patiently.
Reference table
| Keg | Volume | Servings |
|---|---|---|
| Half barrel | 15.5 gal | 157 |
| Quarter barrel | 7.75 gal | 78 |
| Sixth barrel | 5.16 gal | 52 |
| Corny | 5.0 gal | 50 |
| 50 L (metric) | 50 L | 95 at 500 mL |
Limits
- Estimates pours, not party behavior.
- Foam share assumed; systems vary wildly.
- Tasters and half pours shift counts.
- Serve 21-plus with ID checks.
Common mistakes
- Buying by keg count instead of heads.
- Ignoring foam on warm kegs.
- Pouring pints when math assumed 12 oz.
- Skipping the spare for the toast.
- Tapping warm and foamy.
Try it yourself
Quick checks. Answers sit tucked under each question.
Sixth barrel, 16 oz pints, 10 % foam?
Volume is 5.16 x 128 = 660 oz. Good is 594 oz. Servings at 16 oz are 37, foam costs 4.
Quarter barrel, 12 oz, 5 % foam?
Volume is 7.75 x 128 = 992 oz. Good is 942 oz. Servings at 12 oz are 78, foam costs 4.
Questions
What sizes do kegs come in?
Half barrel 15.5 gal, quarter 7.75, sixth 5.16, corny 5.0. Liters abroad run 50, 30, 20. Match the stamp on the keg, not the nickname.
How is the serving count figured?
Gallons times 128 over pour ounces, minus foam share. A half barrel at 12 oz pours about 157 after 5 % foam; pints cut it near 118.
What causes excess foam?
Warm kegs, fast pours, and long lines. Chill 24 hours to 38 F, balance pressure, and pour down the side. Foam loss over 10 % signals system trouble.
Does metric work the same?
Yes: liters times 1000 over milliliters with the same foam share. A 50 L keg at 500 mL pours about 95 after 5 % foam.
How many kegs for a party?
Count heads, multiply by drinks each, divide by servings per keg, then round up and add a spare for the toast. Running dry mid-party costs more than a leftover sixth.
Any legal notes for serving?
Twenty-one and over only, with ID checks and ride plans. Kegs multiply service speed, so staff the pour and watch the room.