Kombucha · Calculator

Kombucha Second Fermentation Calculator

Set fruit juice or priming sugar, and get a carbonation timing window plus a burping plan — so 2F stays fizzy, controlled, and safe.

Start calculating Read the guide
Juice and sugar portions beside kombucha bottles for second fermentation

How to use this calculator

Plan flavoring additions and timing for your second fermentation.

  1. 1

    Set your kombucha volume. Enter the batch volume and select the unit.

  2. 2

    Choose your fermentable source. Select fruit juice or added sugar, then set the juice percentage or sugar per litre.

  3. 3

    Read your bottling plan. Choose carbonation and temperature, then check the addition amount, ready window and bottling steps.

Keep one baseline method for repeatable results. Juice favors flavor integration; added sugar gives a more direct sugar dose.

Live calculator · updates as you type

Your 2F

L
Volume unit
Fermentable source
10%
Target carbonation

Your 2F plan

Fruit juice to add 100ml
Ready windowDay 4–5
Batch volume1.00 L
Burping schedule Burp every 24-36h from day 3
Target carbonation medium
See your 4 bottling steps

What to do next

Bottle it in 4 steps

For your 1 L of finished kombucha.

  1. 1

    Flavour it

    5 min

    Add 100 ml of fruit juice (10% of the batch) to the finished kombucha.

  2. 2

    Bottle and seal

    10 min

    Fill pressure-rated bottles, leaving 2–3 cm of headspace, and seal them.

  3. 3

    Burp and check

    4–5 days

    Keep them at about 24°C. Burp every 24-36h from day 3.

  4. 4

    Chill

    Day 4–5

    When a bottle is fizzy, move every bottle to the fridge. Open over the sink.

Free printable

Keep this batch on one page

A batch card made from your numbers, to save as a PDF or receive by email:

  • Your amounts in big type
  • These steps with tick-boxes
  • Bottling and chilling dates
  • A fizz log for each day

Optional. You can get your PDF without subscribing. Privacy notice.

Carbonation risk rises when fermentables, time, and temperature increase together. Use pressure-rated bottles, stagger your checks, and refrigerate as soon as the target fizz is reached.

Second fermentation guide

Get carbonation without chaos.

Use the calculator to set fermentables and timing, then follow this process framework so carbonation stays intentional, controlled, and repeatable across batches.

Fermentables, time, and temperature drive pressure. Adjust one dial at a time below.

How we calculate: Kombucha methods

Use these reference values to interpret your results

  • Typical window

    2–5 d

    Varies with sugar load, yeast activity, and room temperature.

  • Control lever

    Sugar

    More fermentables can mean faster pressure gain.

  • Safety lever

    Burp

    Release pressure and refrigerate once target fizz is reached.

2F planning model

fermentables + time + temp

Carbonation risk rises when all three increase together. Adjust one dial at a time so you can trace outcomes and keep control.

Set a realistic sugar load for your bottles

Higher fermentable loads can carbonate faster than expected, especially in warm rooms.

Start conservative when changing bottle type, fruit mix, or ambient temperature.

Balance timing and pressure

Short windows produce lighter carbonation while longer warm windows can build pressure quickly.

Always match timing with bottle strength and burping frequency.

Burping schedule is process control

Use earlier and more frequent checks when sugar is high or room temperature is warm.

Refrigerate as soon as carbonation target is reached to slow further pressure rise.

Use bottles rated for pressure

Swing-top or pressure-rated bottles reduce risk compared with decorative or thin glass containers.

Uniform bottle type improves consistency across a batch.

Safety and repeatability

Do not leave highly active bottles unattended in hot spaces for extended periods.

Use logs, staged checks, and refrigeration to control carbonation safely and repeatably.

BottlesSwing-top or pressure-rated glass, filled with consistent headspace.
ChecksBurp on schedule; a firm bottle or hiss means pressure is building.
Chill pointRefrigerate the moment target fizz is reached to halt pressure rise.
Warm roomsAbove 25°C, shorten the window and burp daily from day 2.

FAQ

Second fermentation questions

Common questions about carbonation, fermentables, and safety.

How long should second fermentation take?
Often 2 to 5 days, depending on temperature, sugar inputs, and target carbonation.
Juice vs added sugar for 2F?
Juice adds both flavor and fermentables; added sugar offers tighter carbonation control.
How often should I burp bottles?
Higher temperature or higher carbonation targets usually require earlier and more frequent burping.
Why is my kombucha not fizzy after 2F?
Common causes include low fermentables, weak yeast activity, loose seals, or too-short conditioning time.
What is second fermentation in kombucha?
Second fermentation (2F) is a sealed, room-temperature stage after the main brew. You bottle finished kombucha with a little sugar, juice, or fruit, and the trapped CO2 carbonates the drink while the flavors develop over 2 to 5 days.
How much sugar do you add for second fermentation?
A common starting point is about 1 to 2 teaspoons of sugar, or 10 to 20% fruit juice, per 16 oz (475 mL) bottle. More fermentables mean more fizz and more bottle pressure, so start conservative, burp daily, and adjust the next batch.

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