Free kombucha brewing calculator. Enter your tea volume to find the sugar and starter tea for a standard first fermentation batch.
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Enter your tea volume in litres. The calculator multiplies by 70 grams of sugar and 100 ml of starter tea per litre, the standard first fermentation ratio used on this page. These home brewing steps scale to any batch size, and the sections below cover tea choice and second ferment plans.
A widely used first fermentation recipe uses about 70 grams of sugar and 100 ml of starter tea for every litre of tea, with roughly 2 tea bags per litre. Scaled to a gallon, that is close to 1 cup of sugar, 8 tea bags and 1 to 2 cups of starter liquid. Published recipes vary from about 50 to 100 grams of sugar per litre, so this calculator sits in the middle of the common range.
Starter tea is finished, unflavoured kombucha from a previous batch. It lowers the pH of the fresh sweet tea quickly, which protects the brew from mold and unwanted bacteria. Use at least 10 percent of the batch as starter liquid, and 20 percent for a conservative first batch, so the starter percentage stays between 10 and 20 percent. The SCOBY mat alone is not a substitute for measured starter liquid, because the liquid carries the active culture that starts fermentation.
First ferment usually takes 7 to 14 days at 20 to 23 degrees C, which is about 68 to 80 degrees F. Warmer rooms ferment faster, cooler rooms slower, so taste from day 7 instead of trusting the calendar alone. As the culture works, sweetness falls and tartness rises, and the finished kombucha pH lands near 2.5 to 3.5.
Caffeine varies by tea type. Plain black tea is the most common choice, green tea gives a lighter cup, oolong sits between the two, white tea is the lightest, and herbal or rooibos teas are caffeine free. Fermentation reduces the caffeine from the brewed tea, leaving roughly a third behind, so finished black tea kombucha still contains some caffeine. Avoid flavoured teas and oils in the first ferment, because they can disturb the culture.
Second ferment is the bottled stage where flavor and fizz develop. Common add-ins per 16 oz bottle include fresh ginger, fruit juice, dried fruit, lemon juice or a little honey, each adding a small amount of sugar for the yeast to eat. Seal bottles, keep them at room temperature for 2 to 4 days, burp them daily to release pressure, then refrigerate to stop fermentation and lock in the carbonation.
Brew in clean glass with a tight weave cloth cover secured against fruit flies, and keep the jar out of direct sun. Discard the whole batch and the SCOBY if you see dry, fuzzy mold patches or smell anything rotten, and never scrape mold off and reuse the brew. Brown stringy bits and sediment are normal, but fuzz is not.
This calculator uses 70 grams of sugar per litre of tea. Most published recipes fall between 50 and 100 grams per litre, and one cup of sugar per gallon is the classic rule.
Use at least 10 percent of the batch as starter tea, and 20 percent for a conservative first batch. More starter liquid means a faster, safer start.
About 8 tea bags per gallon, which is roughly 2 bags per litre. Loose leaf works too, at about 8 grams per litre.
Usually 7 to 14 days at 20 to 23 degrees C. Begin tasting from day 7 and bottle when the balance of sweet and tart suits you.
Around 20 to 23 degrees C is ideal. Below that fermentation slows a lot, and above it the brew can turn vinegary fast.
Yes. Green tea makes a lighter, more delicate kombucha, and a black and green blend is a popular middle ground. Avoid herbal and heavily flavoured teas for your first batches.
Second fermentation is bottling the finished kombucha with a little fruit, juice or ginger so it builds carbonation over 2 to 4 days at room temperature.
Dry, fuzzy patches in blue, green, black or white mean mold. Discard the entire batch and SCOBY, since mold cannot be safely scraped away.