Kombucha batch calculator
Kombucha is a fixed ratio ferment: sugar and tea per litre, plus a starter fraction that sets the pH low enough to be safe.
g/L
g/L
%
g/L
Sugar for the sweet tea
238g
- Loose tea
- 17.0
- Or tea bags At about 2 g per bag.
- 8.5
- Sweet tea to brew
- 3.40
- Starter liquid
- 0.60
- Sugar for a second ferment
- 80
- Total sugar
- 318
- Sugar concentration
- 5.95 % w/v
Show the working
- Batch volume = 4
- Sugar = 70
- Tea = 5
- Starter liquid = 15
- Second-ferment sugar = 20
- Starter liquid = 4 * 15/100 = 0.6
- Sweet tea to brew = 4 - 0.6 = 3.4
- Sugar for the sweet tea = 3.4 * 70 = 238
- Loose tea = 3.4 * 5 = 17
- Or tea bags = 17 / 2 = 8.5
- Sugar for a second ferment = 4 * 20 = 80
- Total sugar = 238 + 80 = 318
- Sugar concentration = 4 > 0 ? 238 / (4 * 1000) * 100 : 0 = 5.95
Values are shown to six significant figures here; the arithmetic itself runs on exact fractions and is only rounded where a number is printed.
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The formula
- sweet tea volume = batch volume - starter volume
- sugar = sweet tea volume x sugar rate
At least 10% mature starter liquid is what keeps the pH below 4.2 and the batch safe from mould. Do not skimp on it.
Second fermentation in a sealed bottle builds real pressure. Use bottles rated for it and burp them.