What this calculator does
Priming sugar gives bottled beer its carbonation. The yeast ferments the added sugar in the sealed bottle and the carbon dioxide has nowhere to go. The amount needed depends on the target carbonation, the beer volume and, importantly, the temperature the beer reached during fermentation.
Temperature matters because beer already holds dissolved CO₂, and warm beer holds less. At 68°F the residual is about 0.86 volumes, so only the difference between that and the target has to be supplied by sugar. Ignoring the residual over-primes the beer, and over-priming is how bottles burst.
The formula
The residual CO₂ already dissolved in the beer is calculated from the highest temperature it reached after fermentation. The sugar required supplies the difference between that residual and the target carbonation, scaled by the beer volume and divided by a factor for the sugar type, since different sugars yield different amounts of CO₂ per gram.
| Term | Meaning |
|---|---|
| Volumes of CO₂ | The standard carbonation measure: volumes of gas per volume of beer. Most ales sit at 2.0 to 2.5. |
| Residual CO₂ | Gas already dissolved in the beer, determined by the highest temperature it reached after fermentation. |
| Sugar factor | The relative CO₂ yield per gram: sucrose 1.0, dextrose 0.91, dry malt extract 0.68, honey 0.78. |
The inputs explained
| Field | What to enter |
|---|---|
| Beer volume (US gal) | Beer volume in US gallons. |
| Beer temperature (highest point since fermentation) (°F) | The highest temperature the beer reached after fermentation, in Fahrenheit. This sets the residual CO₂, and using a lower figure than the beer actually reached will over-prime it. |
| Target carbonation (vol CO₂) | Target carbonation in volumes of CO₂. 2.0 to 2.5 covers most ales; wheat beers and Belgian styles go higher. |
| Sugar type | The priming sugar type, which changes the mass needed because the sugars differ in CO₂ yield. |
When to use it
Bottling a batch of homebrew
The standard use. The sugar is boiled in a little water, cooled and mixed into the bottling bucket so it is evenly distributed before filling.
Matching a style carbonation
Styles differ considerably: British ales around 1.5 to 2.0 volumes, American ales 2.2 to 2.7, wheat beers 3.0 and above. Targeting the style is what the carbonation input is for.
Substituting a different sugar
Dry malt extract and honey yield less CO₂ per gram than table sugar, so more is needed, and the factor handles the conversion.
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
How much of each sugar type is needed?
The same batch primed with each of the four sugar types.
| Sugar type | Priming sugar needed | In ounces | Residual CO₂ already in the beer |
|---|---|---|---|
| Table sugar (sucrose) | 116.9 g | 4.12 oz | 0.861 vol |
| Corn sugar (dextrose) | 128.4 g | 4.53 oz | 0.861 vol |
| Dry malt extract | 171.9 g | 6.06 oz | 0.861 vol |
| Honey | 149.9 g | 5.29 oz | 0.861 vol |
Questions
How much priming sugar per bottle?
Work it out for the batch and mix it into the bottling bucket rather than dosing individual bottles. Per-bottle dosing is far less even, and uneven priming means some bottles are flat while others are dangerously over-carbonated.
Why does temperature matter?
Because beer retains dissolved CO₂ from fermentation, and how much depends on the highest temperature it reached afterwards. Warm beer holds less, so it needs more sugar. Using a temperature lower than the beer actually reached overstates the residual and under-primes it; the dangerous error is the reverse.
What happens if I use too much sugar?
Over-carbonation, gushing on opening, and in the worst case bottles failing under pressure. Bottle bombs are a real hazard and the reason to calculate rather than estimate. If you suspect over-priming, refrigerate the bottles, which slows the yeast, and open them carefully over a sink.
How long does bottle conditioning take?
Typically two to three weeks at room temperature, around 20°C. Colder conditions slow the yeast considerably. Chilling the bottles before the yeast has finished will leave the beer under-carbonated until it warms again.
For alcohol content from gravity readings, see the ABV from gravity calculator. For sulphite levels in wine, see the molecular SO2 calculator.