Three numbers between the recipe and the crate
A recipe says five gallons and people count bottles from that, which gives 53 twelve ounce bottles and is wrong in a predictable direction. The volume that reaches the bottling bucket is less than the volume in the fermenter, because the yeast cake, the trub and the last inch the siphon cannot reach all stay behind. Three percent is a modest figure for that and it is worth measuring rather than assuming, because it varies with the vessel, the racking cane and how carefully the transfer went.
Work the default through. Five and a half gallons in the fermenter, three percent lost, leaves 5.34 gallons — 683 fluid ounces. Two and a half gallons of that goes into a keg, leaving 2.84 gallons, which is 363 ounces, which is 30 full twelve ounce bottles and one that comes out short. Not 53, and not 30 either: 31 bottles get filled and 31 caps get used, which is the number that matters when you are counting caps.
That distinction between full bottles and filled bottles is small and it is the one that runs you out of caps. The calculator counts both and uses the filled count for anything you buy per bottle.
The short bottle is a real thing, not a rounding error
Almost every batch ends with a bottle that is not full, because the volume that reaches the bucket is not a whole number of bottles. On the default it is 2.9 ounces in a twelve ounce bottle. That bottle is different from the others in a way worth knowing about: it carries far more headspace, and the beer in it is in contact with far more air.
What that means for the beer over months is a genuine question and this page does not answer it, in either direction. The arithmetic point is simply that the bottle exists, that it is not the same as the other thirty, and that it is not a rounding artefact you can ignore in the count — it still takes a cap.
Splitting between kegs and bottles
The reason people split a batch is that the two packaging routes have opposite problems. A keg is one operation and then the beer is done; it is also one vessel, so the whole thing is committed to one carbonation level and one place. Bottles are an evening of work and they travel, keep independently, and let you carbonate one part of a batch differently from another.
| Split of 5.34 gal packaged | Kegs | 12 oz bottles filled |
|---|---|---|
| All bottles | 0 | 57 |
| One 2.5 gal keg | 1 | 31 |
| One 3 gal keg | 1 | 25 |
| One 5 gal keg | 1 | 4 |
| Two 2.5 gal kegs | 2 | 4 |
Read the last two rows and the arithmetic gets blunt fast. A five gallon keg takes almost the whole batch, and what is left is not a case of beer, it is four bottles. If you want a meaningful number of bottles alongside a keg, the keg has to be the small one.
Cost, and why it is done in whole cents
Money that has to reconcile is calculated in integer cents rather than in dollars, because floating point arithmetic on dollars produces totals that are a cent out and no amount of formatting hides it. Every figure in the cost section is an integer number of cents, and the split between the kegs and the bottles is done by allocating the ingredient cost to the kegs in proportion to volume and then deriving the bottle share as everything left over. That guarantees the two halves add back to the total exactly, which they would not if both were rounded independently.
The per-unit figures are a different kind of number and the page says so. Cost per bottle is a total divided by a count and rounded, which means multiplying it back by the count lands near the total rather than on it. That is not an error; it is what a rate is. The reconciling figures are the totals.
What the cost section deliberately excludes is equipment. A keg, a capper, a bottling bucket and a cylinder are all costs that belong to the hobby rather than to the batch, and spreading them over one batch produces a number that says more about how new your setup is than about what the beer cost. Ingredients and consumables are what actually varies from batch to batch.
Questions people ask
How many bottles does a five gallon batch fill?
Fewer than the 53 that five gallons divided by twelve ounces suggests, because you never package the whole five gallons. At a three percent loss the packaged volume is 4.85 gallons, which is 621 ounces, which is 51 full twelve ounce bottles plus a short one — so 52 caps. At a more realistic six or seven percent loss on a batch racked off a heavy yeast cake it drops to about 50. The single input that decides it is the loss figure, and the only way to have a real one is to measure the difference between what you thought was in the fermenter and what you actually filled.
How many 12 oz bottles is a five gallon keg?
A five gallon keg holds 640 fluid ounces, which is 53 full twelve ounce bottles worth of beer. The practical consequence when you are splitting a batch is that a five gallon keg swallows essentially the whole of a standard batch, so if you want bottles as well the keg has to be a smaller one. The table in the guide above shows the split: a 2.5 gallon keg leaves you 31 bottles from a 5.5 gallon batch, and a five gallon keg leaves four.
What packaging loss should I use?
Whatever yours is, which is why the field exists and why this page suggests nothing. Three percent is a light loss and applies to a clean transfer off a compact yeast cake with a well-placed racking cane. Six or seven percent is unremarkable, and more than that happens with a heavily dry-hopped beer or a fermenter whose geometry leaves a lot below the pickup. Measure it once by noting the fermenter volume and then adding up what you actually packaged, and use that figure from then on.
Why does the calculator count caps from filled bottles rather than full ones?
Because the short bottle takes a cap like every other bottle. It is a small distinction and it is exactly the kind that leaves you one cap short at the end of an evening. The same logic applies to anything else bought per bottle — labels, if you use them, and the bottles themselves if you are buying rather than reusing. Full bottles are the count for how much beer you have; filled bottles are the count for everything you have to buy.
Does the cost per bottle include my equipment?
No, and that is deliberate. Ingredients and consumables are what change from batch to batch; a capper, a bottling bucket, kegs and a gas cylinder are one-off costs that belong to the setup rather than to any particular beer. Amortising them across a batch produces a figure that mostly reports how recently you bought the equipment. If you want that number, work out your total setup cost separately and divide it by however many batches you expect to make, which is a different calculation with a different and much less certain input.