Kombucha Calculator
Tea, sugar, starter and water for any batch size, then the second ferment: flavourings, carbonation pressure and the alcohol it adds. Start from one of our recipes or enter your own.
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Kombucha ratios by batch size
Per gallon of finished kombucha: about 200 g (1 cup) of sugar, 8–10 g of loose tea, and 10–15% of the batch as starter liquid from your last batch. The water figure leaves room for the sugar once it dissolves and for the water the tea leaves hold back. Here it is for each Unitank, at 9 g of tea per gallon and 12% starter.
| Tank | Batch | Water to heat | Tea | Sugar | Starter (12%) |
|---|---|---|---|---|---|
| Unitank 8 gal | 5 gal (19 L) | 4.3 gal (16.2 L) | 45 g | 1.0 kg (2.2 lb) | 0.6 gal (2.3 L) |
| Unitank 13 gal | 10 gal (38 L) | 8.5 gal (32.3 L) | 90 g | 2.0 kg (4.4 lb) | 1.2 gal (4.5 L) |
| Unitank 26 gal | 20 gal (76 L) | 17.1 gal (64.7 L) | 180 g | 4.0 kg (8.8 lb) | 2.4 gal (9.1 L) |
| Unitank 1 BBL | 31 gal (117 L) | 26.5 gal (100.3 L) | 279 g | 6.2 kg (13.7 lb) | 3.7 gal (14.1 L) |
Temperatures and times
Kombucha is a warm fermentation: most of the time you are holding the tank warm, not cooling it. The only cold step is the crash at the end, which stops the yeast so the sweetness, acidity and alcohol stop changing.
| Stage | Temperature | Time |
|---|---|---|
| Steep the tea | 195–200°F black · 175°F green | 10–15 minutes |
| Add the culture | below 85°F | — |
| First ferment | 75–80°F | 7–14 days |
| Second ferment | 72–78°F | 2–5 days |
| Cold crash | 34–38°F | 1–2 days, then keep cold |
Kombucha carbonation chart
Gauge pressure in psi at sea level to hold each carbonation level. Warm, a second ferment under a spunding valve at 10–12 psi only reaches about 1.3 volumes; the fizz most people want, 2.5 to 3 volumes, takes 30 psi or more while warm, so finish carbonating cold after the crash. A Unitank ships with a 15 psi relief valve and is rated to 30 psi.
| Temp | 2.5 vol | 2.8 vol | 3.0 vol | 3.5 vol |
|---|---|---|---|---|
| 34°F1°C | 9 | 12 | 14 | 19 |
| 36°F2°C | 10 | 13 | 15 | 20 |
| 38°F3°C | 11 | 14 | 16 | 22 |
| 40°F4°C | 12 | 16 | 18 | 23 |
| 45°F7°C | 15 | 18 | 21 | 27 |
| 50°F10°C | 18 | 21 | 24 | 30 |
| 60°F16°C | 23 | 27 | 30 | 37 |
| 70°F21°C | 29 | 34 | 37 | 45 |
| 75°F24°C | 32 | 37 | 40 | 49 |
Kombucha recipes
Every recipe opens in this calculator and scales from 5 to 31 gallons. See them all in kombucha recipes, and the whole process step by step in how to make kombucha in a stainless fermenter.
- Classic Black Tea Kombucha: Bright, tart and lightly sweet, with a little apple-cider note from the black tea.
- Green Tea Kombucha: Pale gold, light and crisp, with a softer acidity than the black tea version.
- Half Black, Half Green House Blend: Rounder than green, brighter than black: the most versatile base.
- Ginger Lemon Kombucha: Spicy and bright. More ginger, more heat: 60 g per gallon is fiery.
- Raspberry Hibiscus Kombucha: Deep red, berry-tart and floral. Strain before kegging; raspberry seeds go everywhere.
- Blueberry Basil Kombucha: Purple, jammy and herbal. Take the basil out after two days or it turns grassy.
- Strawberry Lemonade Kombucha: Pink, fruity and sharp, like a lightly sweet sparkling lemonade.
- Pineapple Mint Kombucha: Tropical and cooling. Fizzes fast: pineapple ferments eagerly, so watch the gauge.
- Apple Cinnamon Kombucha: Like a dry, sparkling spiced cider without the alcohol.
- Cherry Vanilla Kombucha: Dark red, tart and smooth, with vanilla on the finish.
- Mango Turmeric Kombucha: Thick, golden and tropical, with a gentle earthy warmth from the turmeric.
- Peach Jasmine Kombucha: Floral and juicy, with a soft peach finish.
How much sugar do I need per gallon of kombucha?
About 200 g, or 1 cup of white sugar, per gallon of finished kombucha (about 53 g per litre). Less than about 120 g per gallon can leave the culture short of food; much more stays sweet for longer.
How much tea per gallon of kombucha?
8–10 g of loose black or green tea per gallon, or four to five tea bags. Use plain tea from the tea plant; teas flavoured with oils can harm the culture.
How much starter liquid do I need?
At least 10% of the batch, and 10–15% is the usual range: for 5 gallons, about 2 to 3 litres of plain kombucha from your last batch. The starter drops the pH below 4.6 straight away, which is what keeps mould out.
How long does kombucha take to ferment?
The first ferment takes 7 to 14 days at 75–80°F: closer to 7 when warm, 14 or more when cool. The second ferment, for flavour and fizz, takes 2 to 5 days at 72–78°F.
What pressure carbonates kombucha?
It depends on temperature. At 36°F, about 13 psi gives 2.8 volumes; warm, the same fizz would take over 30 psi. That’s why kombucha is spunded at 10–12 psi during the second ferment and finished cold after the crash. The chart above has every combination.
How much alcohol does kombucha have?
The first ferment usually leaves 0.2–1% ABV, and every gram of sugar per litre that ferments in the second ferment adds about 0.065%. In the US, 0.5% ABV or more is regulated as alcohol, so commercial producers crash cold, keep it cold, and test every batch.