Updated March 2026.
A US half-barrel keg — the one people mean by “a keg” — holds 15.5 US gallons, or 1,984 fluid ounces. That is 165 twelve-ounce beers, or 124 sixteen-ounce pints, before foam and the unpourable heel. A quarter-barrel (“pony”) is 7.75 gallons / 992 ounces. A sixth-barrel (“sixtel”) is about 5.16 gallons / 661 ounces. TTB treats a beer barrel as 31 US gallons.
Ask for the size on the invoice. A 50-liter import keg is not a half-barrel. See how much a keg costs.
US keg sizes in ounces
| Keg | US gallons | Fluid ounces | 12 oz | 16 oz | 20 oz | Barrel fraction |
|---|---|---|---|---|---|---|
| Full barrel (rare at retail) | 31 | 3,968 | 331 | 248 | 198 | 1 |
| Half barrel / “full keg” | 15.5 | 1,984 | 165 | 124 | 99 | 1/2 |
| 50-liter import | 13.2 | 1,691 | 141 | 106 | 85 | 50 L in § 25.156 |
| Quarter barrel / pony | 7.75 | 992 | 83 | 62 | 50 | 1/4 |
| 30-liter keg | 7.93 | 1,014 | 85 | 63 | 51 | 30 L in § 25.156 |
| Sixth barrel / sixtel | 5.16 | 661 | 55 | 41 | 33 | 1/6 |
| Cornelius / “corny” | 5.0 | 640 | 53 | 40 | 32 | 5-gal listed |
| Eighth barrel | 3.875 | 496 | 41 | 31 | 25 | 1/8 |
| Mini keg / “Bubba” | 1.32 | 169 | 14 | 11 | 8 | ~5 L single-use |
Ounces: 1 US gallon = 128 fl oz, so 15.5 × 128 = 1,984. The sixth-barrel is 31 ÷ 6 = 5.1667 gallons × 128 ≈ 661 oz. TTB’s beer FAQ states one barrel equals 31 U.S. gallons and points to 27 CFR 25.156 for keg tax equivalents.
What you actually pour
Those 165 twelves assume every ounce leaves the keg as beer. Foam, a badly packed coupler, and the last unpourable inch steal servings. Plan on losing a few beers, not gaining them. A party cup marked 16 ounces is often filled to 12–14. For pitcher math see how much is in a pitcher of beer. For weight, how much a case of beer weighs is a different container.
European 50 L kegs show up under import brands. They are not half-barrels. If the invoice says 50 L, use 1,691 ounces, not 1,984.
Keg vs case
A half-barrel’s 1,984 ounces ÷ 288 ounces in a 24-pack of 12-ounce cans ≈ 6.9 cases. A sixtel is about 2.3 cases. That is volume, not a price list. Deposit, coupler type (D-system Sankey is the US standard for most domestic lagers; other brands use S, A, G, or U) and whether the shop sells the tap are separate from the ounce count.
Pints, cups, and the leftover inch
US bars sell a pint as 16 ounces. A UK-style 20-ounce imperial pint pour from a half-barrel is about 99 glasses. Metric 50 L kegs are billed as 50 L, which is 1,690.7 US fl oz if you convert 1 L = 33.814 oz. TTB’s 50-liter barrel equivalent in § 25.156 is tax math, not a different physical keg.
Sixth-barrels are the craft-bar default because they fit more brands on one box. Two sixtels are 10.33 gallons, still short of a half-barrel’s 15.5. Do not order “a keg” on the phone without naming the size.
Weight is not ounces, but people ask
A full half-barrel is often cited around 160 pounds (beer plus the steel). A sixtel full is often cited around 55–60 pounds. Those are industry rules of thumb, not a TTB weight. The ounce count does not change if the keg is stainless or a one-way PET. Foam still steals glasses.
More in our Bar Basics.
Sources
- TTB Beer FAQ B2: one barrel equals 31 U.S. gallons; see 27 CFR 25.156.
- 27 CFR 25.11: barrel, as a unit, = 31 US gallons.
- 27 CFR 25.156: authorized keg fractions and metric sizes for tax computation.
- US gallon = 128 fl oz (NIST Handbook 44 / customary units).