Kombucha's tea-to-sugar-to-starter ratio is simple, but it's easy to get wrong when scaling a recipe up or down for a bigger jar or a bigger batch. This calculator applies the standard per-gallon ratio to your exact batch volume so you always brew with the right proportions.
How the Kombucha Ratio Calculator works
The calculator starts from the widely used home-brewing baseline: 1 cup of white sugar, 8 tea bags (or about 2 tablespoons of loose black or green tea), and 2 cups of starter liquid per gallon of finished batch. Every amount scales directly with your target batch volume — a 3-gallon batch simply triples each ingredient.
Choosing Strong strength increases the tea amount by roughly 25% to produce a tangier, more caffeinated brew, while sugar and starter liquid stay at their standard ratio since those govern the SCOBY's food supply and the batch's protective acidity, not its flavor intensity.
Inputs and what they mean
Batch volume is the total finished kombucha you're brewing, in gallons, including the starter liquid you add. Most home brewers start with a 1-gallon glass jar and scale up once they're comfortable with the process.
Brew strength is a Standard-or-Strong toggle. Standard follows the classic ratio; Strong steeps more tea for a bolder, tangier result. Neither setting changes the sugar or starter amounts, since those relate to feeding the SCOBY and preventing contamination, not to flavor strength.
Limits and edge cases
This calculator scales the standard first-ferment ratio; it doesn't model flavor additions, temperature, brew time, or a second ferment (bottling with fruit or juice for carbonation), which is a separate process with its own timing and ratios. Very large batches are mostly limited by vessel size and SCOBY size, not by the math — the ratios themselves keep scaling linearly. If you're using a much smaller or larger SCOBY than the batch calls for, fermentation speed (not the ingredient ratio) is what changes.