Fermentation Sugar Calculator
Fermentation converts sugars to alcohol and carbon dioxide. Homebrewers and fermenters use two main calculations: how much priming sugar to add for bottle carbonation, and what ABV their ferment achieved based on the change in gravity. This calculator handles both. For priming sugar, enter the batch volume, desired CO2 volumes (2.4 is a standard American ale), beer temperature, and sugar type. For ABV, enter the original gravity (OG) before fermentation and the final gravity (FG) after. The ABV formula used is the simplified but accurate Brewers Association standard: ABV = (OG - FG) * 131.25.
Fermentation formulas
ABV (%) = (OG - FG) * 131.25
Attenuation (%) = (OG - FG) / (OG - 1) * 100
Dissolved CO2 (volumes) = 3.0378 - 0.050062 * tempF + 0.00026555 * tempF^2
Priming sugar (oz dextrose) = 0.53 * gallons * (target CO2 - dissolved CO2) * sugar_factor
Carbonation levels by style
- British ales (cask): 1.0-1.5 volumes CO2
- American ales: 2.2-2.7 volumes CO2
- German lagers, Belgian ales: 2.4-3.0 volumes CO2
- Wheat beers, kombucha: 2.8-4.0 volumes CO2
- Champagne, hard cider: 3.0-5.0 volumes CO2
Fermentation sugar: frequently asked questions
How much priming sugar do I need to carbonate beer?
The standard rate is 0.53 oz (15 g) of corn sugar (dextrose) per gallon of beer for about 2.5 volumes of CO2, which is typical for most American ales. The exact amount varies by desired carbonation level (volumes of CO2) and beer temperature at bottling.
Why does temperature affect priming sugar amount?
Yeast converts sugar to equal parts CO2 and alcohol. At lower temperatures, beer retains more dissolved CO2 from fermentation. If beer was cold-conditioned near 32 F, it already holds more CO2 and needs less priming sugar. Warmer beer needs more sugar to reach the same carbonation level.
How do I calculate potential ABV from gravity?
ABV = (OG - FG) * 131.25, where OG is original gravity and FG is final gravity (both in specific gravity units like 1.050). This formula gives a good approximation up to about 10% ABV. More precise formulas exist for high-alcohol fermentations.
What is the difference between corn sugar and table sugar for priming?
Corn sugar (dextrose) is 100% fermentable and is the standard priming sugar. Table sugar (sucrose) is also fully fermentable but contains a tiny amount of residual compounds. Use 0.53 oz dextrose or 0.48 oz sucrose per gallon for equivalent carbonation. Honey adds flavor and is about 80% fermentable.
Can I use priming sugar calculators for kombucha or hard cider?
Yes. The same CO2 volume principles apply to kombucha and hard cider. Kombucha is typically carbonated to 2.5-3.5 volumes CO2; hard cider to 2-3 volumes. Adjust the carbonation volumes target in the calculator. Kombucha and cider may ferment faster than beer, so monitor bottles carefully.
Official sources
- Brewers Association: Brewers Association Technical Resources.
- TTB: TTB Beer Regulations.
Reviewed by the CalculatorHub team, edited by James Graham, 14 June 2026. See our methodology.