What a keg actually holds
Every keg calculation starts from the US beer barrel, which the Alcohol and Tobacco Tax and Trade Bureau defines in 27 CFR part 25 as 31 US gallons. Every American keg size is a fraction of that barrel, and none of them is a round number of gallons except by coincidence:
- Half barrel — 15.5 gal, 1,984 fl oz, 58.67 L. The standard bar keg, about 161 lb full.
- Quarter barrel — 7.75 gal, 992 fl oz. Sold as a short “pony” or a tall “slim quarter”; both hold the same beer.
- Sixth barrel (sixtel) — 5.16 gal, about 660 fl oz. The craft standard, because it fits more taps into the same cooler.
- Cornelius keg — 5 gal, 640 fl oz. A repurposed soft-drink container used by homebrewers.
- Import kegs — 50 L (1,690.7 fl oz), 30 L and 20 L, used by most European brewers.
The number people quote from memory is almost always wrong in the same direction. “About 140 pints in a keg” is a half barrel divided by 14 ounces, not 16; “165 beers” is a half barrel at a 12 oz pour with zero loss. Both are real answers to different questions, which is why you have to fix the glass size before the keg number means anything.
Why the answer is a floor, and what the loss term really covers
The formula divides sellable volume by pour size and takes the floor. Both of those choices carry weight.
The loss term is where the estimate lives or dies. It absorbs four separate things: beer foamed off during the pour, beer purged when a line is cleaned or a keg changed, tasters given away at the tap, and the beer left in the keg when the pour turns to foam and the keg is pulled. On a balanced system with correct line length, correct applied CO2 pressure for the beer's carbonation level, and a cooler at serving temperature, that total is small. On an unbalanced system it can be the difference between a profitable tap and a break-even one, because every one percent of loss on a half barrel is roughly 20 fluid ounces of beer you bought and cannot sell.
The floor matters because a partial glass is not a sale. If sellable volume is 1,884.8 fl oz and the glass is 16 fl oz, the arithmetic gives 117.8 — but the 0.8 of a glass at the end goes down the drain, so the honest answer is 117.
There is one more subtlety that trips up new operators. A “16 oz” American shaker pint is a 16 fl oz glass to the brim; filled with beer and a proper head, it delivers noticeably less liquid. If your loss figure is calibrated against actual keg yields rather than guessed, that shortfall is already inside it. If you enter a glass capacity and a loss figure separately, be careful not to count the head twice.
Worked example: a $150 half barrel at $7 a pint
You buy a half barrel for $150 delivered, pour it into 16 fl oz glasses, allow 5% for foam and line loss, and sell each glass for $7.
- Keg volume. 15.5 gal × 128 fl oz per gallon = 1,984 fl oz.
- Sellable volume. 1,984 × (1 − 0.05) = 1,884.8 fl oz.
- Servings. 1,884.8 ÷ 16 = 117.8, floored to 117 pints.
- Cost per pour. $150 ÷ 117 = $1.2821.
- Pour cost. $1.2821 ÷ $7.00 = 0.18315, or 18.3%.
- Revenue. 117 × $7.00 = $819.
- Gross profit. $819 − $150 = $669 per keg.
Now see what the loss allowance is worth. At zero loss the same keg gives 124 pints, $868 of revenue and $718 of profit. The five percentage points of loss cost you seven pints and $49 — on a bar pouring ten kegs a week, that is $490 a week, or the price of a line-cleaning contract several times over.
And check the sensitivity to glass size. Drop from a 16 oz pour to a 14 oz pour on the same keg and the yield rises from 117 to 134 servings. If you can hold the price, that is $119 of extra revenue from exactly the same purchase — which is why glass size is a pricing decision, not a service detail.
How to read pour cost and gross profit
Pour cost is the share of each sales dollar that goes to buying the liquid. It is the beverage twin of food cost percentage, and it is the number a bar manager watches weekly. Beverage cost control texts put typical draught beer targets in the low twenties as a percentage of sales, with bottled beer usually higher and spirits usually lower, because a spirit pour carries a much larger mark-up. Where your own target sits depends on your rent, your labour and what your market will bear — but if the figure this calculator gives you is far above your target, only three levers exist: pay less for the keg, sell for more, or lose less beer.
Gross profit per keg is what the tap contributes before labour, CO2, glass washing, waste and the keg deposit. It is not the profit on the tap. Two kegs with identical pour cost can produce very different gross profit if one is a $150 domestic half barrel and the other a $220 sixtel: the sixtel has a third of the volume, so it must be priced far higher per pour just to keep pace.
Read the servings figure as a ceiling rather than a forecast. It assumes the keg sells out cleanly before the beer goes stale on the line. A slow-moving tap on a sixth barrel is a better bet than a slow-moving tap on a half barrel for exactly that reason. If you are costing a whole beverage programme rather than one keg, the food cost percentage calculator and the menu price calculator work the same arithmetic from the other direction — pick a target cost percentage and get the price.
Servings per keg by size and glass, before any loss
| Keg | Volume (fl oz) | 10 oz | 12 oz | 16 oz | 20 oz |
|---|---|---|---|---|---|
| Half barrel (15.5 gal) | 1,984 | 198 | 165 | 124 | 99 |
| Quarter barrel (7.75 gal) | 992 | 99 | 82 | 62 | 49 |
| Sixth barrel (5.16 gal) | 660.5 | 66 | 55 | 41 | 33 |
| Cornelius (5 gal) | 640 | 64 | 53 | 40 | 32 |
| Import (50 L) | 1,690.7 | 169 | 140 | 105 | 84 |
| Import (30 L) | 1,014.4 | 101 | 84 | 63 | 50 |
| Import (20 L) | 676.3 | 67 | 56 | 42 | 33 |
Metric kegs converted at 33.8140 fl oz per litre. US barrel = 31 gal per 27 CFR part 25.
What makes a keg yield less than the arithmetic says
- Unbalanced draught lines. Line resistance has to match applied CO2 pressure. Too little resistance and every pour foams; too much and the pour crawls and the server tops it up from a second glass.
- Warm beer anywhere in the run. Beer above about 40 °F breaks out CO2 and foams at the faucet. A cooler at the right temperature with a warm trunk line still foams.
- Wrong applied pressure for the beer's carbonation. Under-pressurising flattens the beer and eventually foams as CO2 comes out of solution; over-pressurising over-carbonates it. Set pressure from the beer's target volumes of CO2 and the cooler temperature — the keg carbonation PSI calculator gives the right number.
- Line cleaning and keg changes. Every clean purges a full line of beer, and every keg change costs a partial pour. On a long trunk line that is meaningful volume, and it is a fixed cost per keg rather than per ounce.
- Free tasters. A taproom that pours three one-ounce samples per keg-hour is giving away real beer. Count it in the loss figure rather than pretending it is marketing.
- Over-pouring by hand. Free-pouring into a 16 oz glass with no fill line drifts upward over a shift. A lined glass costs a few cents and pays for itself in one keg.
- Confusing keg deposit with keg cost. The deposit is refundable and does not belong in your cost per pour; the delivery charge does.
Kegs for a party, not a bar
If you are renting a keg for an event rather than running a tap, two numbers change. First, use a higher loss allowance: a picnic-pump keg served over ice runs warm, foams heavily, and goes flat because a hand pump pushes air rather than CO2, so plan on losing noticeably more than a balanced bar system does. Second, size the keg from a drink count rather than a volume. Work out the drinks you need in the party and wedding alcohol calculator, then convert: a half barrel at a 12 oz cup covers about 165 beers before loss, so a 100-guest four-hour party at a 40% beer share needs roughly one half barrel.
Where this fits among the other draught numbers
Servings per keg is the first of three numbers a draught programme needs, and it is the only one that is pure arithmetic.
The second is carbonation and pressure. Getting a keg to pour cleanly is a physics problem involving the beer's dissolved CO2, the cooler temperature and the resistance of the line. Solve it and your loss figure falls; ignore it and no amount of pricing fixes the yield.
The third is what is in the keg. If you are brewing your own, the yield question runs backwards from grain to finished beer, and the relevant tools are the brewhouse efficiency calculator for how much extract you got out of the mash and the beer ABV calculator for what the fermentation produced. A homebrewer filling Cornelius kegs should note the 640 fl oz figure above: five gallons is 40 pints before any loss, and after transfer losses and trub it is usually closer to 36.
One conversion note for anyone working across systems. A US fluid ounce is 29.5735 mL and a US gallon is 128 fl oz, so a 50 L import keg is 13.209 US gallons — noticeably less than a half barrel, despite the two often being priced similarly. If a distributor quotes you an import keg and a domestic half barrel at the same price, the import is 15% more expensive per ounce.
Key terms
- Barrel (bbl)
- The US beer barrel, 31 US gallons, as defined for tax purposes in 27 CFR part 25. Keg sizes are named as fractions of it.
- Sixtel
- A sixth-barrel keg, nominally 5.16 US gallons. Same footprint as a Cornelius keg but taller, and the standard package for craft beer.
- Pour cost
- Cost of the liquid in one serving divided by its menu price, expressed as a percentage. The beverage equivalent of food cost percentage.
- Line balance
- Matching the resistance of the beer line to the applied gas pressure so beer arrives at the faucet at the right speed without foaming.
- Keg deposit
- A refundable charge for the container itself. It is working capital, not a cost of goods, and should be kept out of pour cost.