01
Choose your fermentable source
Use juice mode when flavor integration is the priority and sugar mode when pressure control is the priority.
Both approaches work, but consistency is better when you keep one baseline method.
Kombucha · Second Fermentation Calculator
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.
Carbonation dials
2–5 days
Fermentablesjuice / sugar
Ready window2–5 d
Burp + chillsafety
Fermentables, time, and temperature drive pressure. Adjust one dial at a time below.
Live calculator · updates as you type
Your 2F
L
10%
Target carbonationYour 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
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.
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.
02
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.
03
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.
04
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.
05
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.
06 Safety
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.
Download the free Kombucha Brewing Schedule
Use the printable 2F checklist for sugar inputs, burping timing, and bottle safety tracking.
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.
Keep brewing
Continue your kombucha workflow
Sugar calculator Estimate residual sugar before you plan bottle pressure. Brewing calculator Set sugar, tea, and starter for any batch with a 1F estimate. Batch calculator Scale a known recipe from 1L to 25L with ratios locked. All kombucha guides Browse every kombucha calculator and brewing guide in one place.