Basics and units
Forced carbonation pressure
2.5 volumes at 4 °C? Set 0.83 bar and wait a week. The tool gives the pressure for your temperature and your carbonation.
Result
Fill in the values and run the calculation, or try the example.
This is the calculation Krausi uses. Create an account to save it in a recipe or a brew.
Create my accountWhy does the pressure depend on temperature?
A gas dissolves better in a cold liquid. At the same pressure, a keg at 2 °C absorbs far more CO2 than a keg at 12 °C: the same setting gives an almost flat beer in a cellar and a foaming beer in a fridge.
So to carbonate in a keg, you set the pressure according to two things: the carbonation you want, in volumes of CO2, and the temperature at which the keg will stay. Once equilibrium is reached, the beer keeps this carbonation as long as temperature and pressure do not change.
How is the carbonation pressure calculated?
The equilibrium pressure is given by a polynomial of the temperature T (in °C) and the carbonation, with r = volumes × 1.98:
P (bar) = 0.000260165 × T² + T × (0.0109218 × r + 0.00799664)
− 0.0012163 × (r − 278.507) × (r − 3.22065)It is a gauge pressure, the one the regulator gauge shows. The result is also given in psi.
Carbonation chart: pressure in bar
| Volumes of CO2 | 2 °C | 4 °C | 8 °C | 12 °C |
|---|---|---|---|---|
| 2 vol. | 0.35 bar | 0.46 bar | 0.67 bar | 0.9 bar |
| 2.5 vol. | 0.7 bar | 0.83 bar | 1.09 bar | 1.36 bar |
| 3 vol. | 1.05 bar | 1.2 bar | 1.5 bar | 1.81 bar |
Worked example
Values entered
- Target carbonation in volumes of CO2: 2.5
- Beer temperature in °C: 4
Result from the tool
- Gauge pressure in bar
- 0.83 bar
- Gauge pressure in psi
- 12.01 psi
What the tool does not do
- From 1.5 to 4.3 volumes of CO2 and from 2 to 30 °C.
- Equilibrium takes several days: allow a week at serving pressure, without shaking the keg.
- The carbonation pressure is not always the right serving pressure: the beer line length must balance it.
Frequently asked questions
How long does it take to carbonate a keg?
About a week at equilibrium pressure, without touching anything. You can go faster by raising the pressure for a day or two or by shaking the keg, at the risk of overshooting the target carbonation.
What pressure for an IPA?
An IPA is served at between 1.5 and 2.3 volumes of CO2. At 4 °C, 2.4 volumes need 0.75 bar. The recommended carbonation by style gives the range for each family of beers.
And with the assistant?
Ask Krausi the same question in plain language: he picks this tool, does the calculation and files the result in your project.
My keg is at 4 °C, I want 2.5 volumes. What do I set the regulator to?
Set 0.83 bar (12 psi) and leave the keg for a week at 4 °C. I'm noting the target carbonation of 2.5 volumes in the brew.