How much sugar, juice or fruit goes into each bottle? Set a fizz level, or check the add-in you already use, and see how much CO2 and alcohol that sugar can make in a sealed bottle.
Kombucha Second Fermentation Calculator - Sugar and Fizz
How much sugar, juice or fruit goes into each bottle? Set a fizz level, or check the add-in you already use, and see how much CO2 and alcohol that sugar can make in a sealed bottle.
Parameters
Enter data for calculations
💡 Fill in all required fields to unlock the calculate button
Kombucha second fermentation: how much sugar, how much fizz
A 16 fl oz bottle of kombucha bottled at 72 °F needs about 3.1 g of sugar, a little under 3/4 of a teaspoon, to reach 2.5 volumes of CO2, the fizz of an American lager. This kombucha second fermentation calculator works that out for table sugar, honey, five juices, five fruits and ginger. It also runs the other way: tell it what you already put in each bottle and it shows the highest carbonation and the most alcohol that sugar can make.
Five entries between an empty bottle and a number
- Bottle size and count - fluid ounces or milliliters, from 4 to 64 fl oz, and up to 100 bottles.
- Temperature at bottling - of the kombucha itself, 47 to 83 °F. Warmer kombucha holds less dissolved CO2.
- What you want - a sugar amount for a target fizz, or a check of the add-in you already use.
- Add-in - sugar, honey, apple, grape, pineapple, orange or unsweetened cranberry juice, strawberries, blueberries, raspberries, mango, sweet cherries or fresh ginger.
- Target or amount - light, medium, high or your own number of volumes; or the amount per bottle in teaspoons, tablespoons, fluid ounces, milliliters, grams or ounces.
Problem: a splash of juice that looks small is a lot of pressure
Some home recipes for flavoring kombucha call for up to a quarter cup, 2 fl oz, of juice per bottle. Run that through the numbers: 2 fl oz of apple juice carries about 6 g of sugar, and in a 16 fl oz bottle that sugar alone can add 3.32 volumes of CO2. With what the kombucha already holds, the ceiling is 4.11 volumes, above every style in the Brew Your Own carbonation chart except Belgian ales and German weizens. One level teaspoon of sugar does almost the same: 3.13 volumes. The National Center for Home Food Preservation (NCHFP) warns that kombucha in airtight containers builds up CO2 and can explode if it is not watched.
Solution: count grams of sugar, not days on the counter
Pressure in a sealed bottle can only rise until the yeast has used the sugar it was given. So the calculator sets the sugar first. Sugar per bottle = (target - CO2 already in the kombucha) x 3.80 g per liter x liters. The 3.80 comes straight from the Brew Your Own sucrose table, where 85 g in 19 L adds 1.18 volumes; the chemistry of complete fermentation gives 3.84. The CO2 already present comes from the same chart: 0.85 volumes at 68 °F, 0.728 at 77 °F. Juice and fruit are converted to sugar with USDA FoodData Central values.
You will not find a day count in the result. No extension service publishes a tested schedule for a second fermentation, and temperature changes how fast the sugar is used, not how much CO2 it can make. A warm bottle reaches its ceiling sooner; it does not get a higher one.
How much of each add-in reaches 2.5 volumes
One 16 fl oz bottle at 72 °F needs 3.1 g of sugar. The table shows how much of each add-in brings that much, using total sugars per 100 g from USDA. Sweet juices like grape need less than apple; berries low in sugar need a surprising weight.
| Add-in | Sugar per 100 g | Per 16 fl oz bottle |
|---|---|---|
| Table sugar | 99.8 g | 0.7 tsp (3.1 g) |
| Honey | 82.1 g | 0.5 tsp (3.7 g) |
| Grape juice | 14.2 g | 1.4 tbsp (20 ml) |
| Apple juice | 9.62 g | 2.1 tbsp (30 ml) |
| Orange juice | 8.31 g | 2.4 tbsp (35 ml) |
| Mango | 13.66 g | 22 g (0.8 oz) |
| Blueberries | 9.96 g | 31 g (1.1 oz) |
| Strawberries | 4.89 g | 63 g (2.2 oz) |
| Fresh ginger | 1.7 g | 180 g, not practical |
Ginger is the odd one out: it flavors the bottle but brings almost no sugar, so a ginger bottle fizzes on whatever sugar the kombucha still has, or on sugar added with it.
Teaspoons, splashes and handfuls: the ceiling each one sets
Same 16 fl oz bottle at 72 °F, starting from 0.79 volumes. Alcohol is the most this sugar can add if all of it ferments. The federal Alcohol and Tobacco Tax and Trade Bureau (TTB) treats kombucha at 0.5% alcohol by volume or more, at any time including after bottling, as an alcohol beverage.
| Added per bottle | Sugar | Ceiling, volumes | ABV, at most |
|---|---|---|---|
| 30 g strawberries | 1.5 g | 1.61 | +0.21% |
| 1 oz blueberries | 2.8 g | 2.36 | +0.41% |
| 2 tbsp apple juice | 3.0 g | 2.45 | +0.43% |
| 1 tsp table sugar | 4.2 g | 3.13 | +0.60% |
| 1 tsp honey | 5.7 g | 3.99 | +0.83% |
| 2 fl oz apple juice | 6.0 g | 4.11 | +0.86% |
| 2 fl oz grape juice | 9.0 g | 5.79 | +1.29% |
For reference, Brew Your Own lists British ales at 1.5 to 2.2 volumes, American ales at 2.2 to 3.0, American lagers at 2.5 to 2.8 and German weizens at 2.8 to 5.1. The calculator's light, medium and high settings are 2.0, 2.5 and 3.0.
The sugar you did not add
The calculator counts only the add-in. The first fermentation starts with a lot more: the NCHFP gallon recipe uses 1 cup, about 200 g, of sugar, roughly 53 g per liter. If that much sugar fermented in a sealed bottle it could make about 14 volumes of CO2 and 3.6% alcohol. Most of it is used up in the open jar, which is why the first fermentation runs for 7 to 10 days under a cloth or paper towel, not a lid. Kombucha that still tastes clearly sweet at bottling has some of it left, and that sugar adds pressure on top of the result here.
Second fermentation questions
Related tools
Sauerkraut Calculator
Salt per pound of cabbage, quarts of kraut and fermenting time from the USDA recipe - See the calculator
BBQ Meat Calculator
Raw brisket, pulled pork, ribs or chicken to buy, worked back from cooked portions per guest - See the calculator
Kombucha Calculator
Tea, sugar, water and starter for the first fermentation, from a quart to 5 gallons - See the calculator
Homebrew ABV Calculator
Alcohol by volume from gravity readings - See the calculator
Wine Fermentation Calculator
Primary and secondary fermentation time for a home wine - See the calculator
Sugar Substitute Calculator
Honey, maple syrup or a sweetener in place of sugar - See the calculator
Brine Calculator
Salt for fermenting vegetables and dill pickles - See the calculator
Kitchen Measurement Converter
Cups, tablespoons, grams and milliliters - See the calculator