Kombucha Batch Calculator
Calculate tea, sugar, and starter liquid amounts for any kombucha batch size.
Includes first and second fermentation ratios.
How kombucha ratios work:
Kombucha is fermented sweet tea. A SCOBY (Symbiotic Culture of Bacteria and Yeast) plus acidic starter liquid from a previous batch convert the sugar into organic acids, carbonation, and trace alcohol. The ratios must stay within safe ranges to prevent mold and off-flavors.
Standard first fermentation (F1) ratios:
| Ingredient | Amount per gallon | Purpose |
|---|---|---|
| Water | ~14 cups | Base liquid |
| Tea | 4–6 bags or 2–3 tbsp loose | Provides nitrogen and tannins for the SCOBY |
| Sugar | 1 cup (200g) | Food for the SCOBY — most is consumed |
| Starter liquid | 1–2 cups | Lowers pH to prevent mold |
| SCOBY | 1 per vessel | The living culture |
The golden ratios:
- Sugar: 1 cup per gallon (about 50g per liter)
- Starter liquid: 10–15% of total batch volume
- Tea: 4–6 tea bags per gallon (black, green, or a blend)
Worked example — 1 gallon batch:
- Boil 4 cups water, steep 5 tea bags for 10 minutes
- Dissolve 1 cup (200g) sugar in the hot tea
- Add cold water to fill to 14 cups
- Let cool to below 85°F (30°C)
- Add 2 cups starter liquid + SCOBY
- Cover with cloth, ferment 7–14 days at 72–82°F
Second fermentation (F2) — carbonation:
After F1, bottle the kombucha with added flavor:
- Fruit juice or puree: 10–20% of bottle volume
- Ginger, herbs: 1–2 tbsp per 16 oz bottle
- Seal tightly and leave at room temp for 2–4 days
- Burp bottles daily — pressure can cause glass to explode
- Refrigerate to stop fermentation and hold carbonation
Sugar consumption: The SCOBY consumes 70–90% of the sugar during F1. A finished kombucha typically has 2–5g sugar per 8 oz serving — far less than the 25g+ you started with.
pH safety: Finished kombucha should be pH 2.5–3.5. If pH stays above 4.0 after 7 days, discard the batch — the acid level is too low to prevent harmful bacteria growth.