Packaging

This is the guide for a bottling or kegging calculator: how much priming sugar, what pressure to set the regulator to, and, for cider and wine, how much sulfite.

The functions to start with

• primingSugar answers "how much sugar to carbonate these bottles?" from the volume, the target carbonation, and the warmest temperature the beer reached after fermentation.
• pressureFromCo2Volumes answers "what do I set the regulator to?" from the beer's temperature and the carbonation you want.
• sulfiteDose answers "how much potassium metabisulfite?" from the volume and the pH, for ciders, meads and wines.

The same carbonation three ways

19 L of beer that finished at 20 °C, to be bottled at 2.4 volumes with table sugar:

const bottles = primingSugar({
  beerVolumeL: 19,
  targetVolumes: 2.4,
  fermentationTempC: 20,
  sugar: 'table-sugar',
});
Copy

That's 111 g. The beer already holds 0.86 volumes of CO₂ from fermentation, so the sugar only has to make the rest. Corn sugar, as in Start here, takes 129 g for the same beer, because a gram of it makes less CO₂.

The same 2.4 volumes in a keg at 4 °C:

const kegPsi = pressureFromCo2Volumes(4, 2.4);
const kegBar = psiToBar(kegPsi);
Copy

10.7 PSI, or 0.74 bar.

And 20 L of cider at pH 3.5, sulfited before it's sweetened:

const cider = sulfiteDose({ volumeL: 20, ph: 3.5 });
Copy

The cider has to hold 40 mg/L of free SO₂, which takes 1.39 g of potassium metabisulfite.

The working

primingSugarExplained and forcedCarbonationExplained return the working for the first two. Start here prints the priming explanation line by line. One of its notes is worth knowing before someone asks: a keg gets the same dose as bottles. The common advice to prime a keg with less has no source behind it, and the comment on primingSugar works through why.

sulfiteDoseExplained gives the working for the sulfite, including a note when the pH is too high for sulfite to be practical on its own.

Traps

• Use the warmest temperature, not the current one. Residual CO₂ depends on the warmest the beer got at or after the end of fermentation. A beer that finished at 20 °C and was then cold-crashed to 2 °C still holds only what it held at 20 °C.
• Pressure is in PSI gauge. That's what regulators read. Convert with psiToBar and psiToKilopascals.
• A sulfite dose without a pH is meaningless. The free SO₂ needed rises about sixfold between pH 3.0 and 3.8. If you've already sulfited, pass the free SO₂ you measured as currentFreeSo2MgL. The engine doesn't estimate it, because it binds at a rate you can't compute.
• Sorbate is a separate dose. sorbateDose works from the ABV, and you'll want both before backsweetening.

Going further

Carbonation and packaging, the method page, has the carbonation tables, the residual-CO₂ curve and the sugar yields with their sources. A blend of finished beers primes differently, because sweeter components keep fermenting in the bottle. The Blending guide covers that.