Kombucha Brewing Calculator

What Is Kombucha and Why Brew Your Own?

Kombucha is a fermented tea beverage that has been consumed for thousands of years, originating in Northeast China around 220 BCE. This naturally effervescent drink is made by fermenting sweetened tea with a symbiotic culture of bacteria and yeast, commonly known as a SCOBY (Symbiotic Culture Of Bacteria and Yeast). The fermentation process transforms sweet tea into a tangy, slightly vinegary probiotic drink packed with beneficial acids, enzymes, and live cultures.

Brewing kombucha at home offers numerous advantages over store-bought varieties. Commercial kombucha typically costs $3-5 per bottle, while homemade kombucha costs mere pennies per serving. More importantly, you have complete control over the fermentation time, sugar content, and flavor profile. Many home brewers report that their homemade kombucha tastes fresher and more nuanced than commercial alternatives, with better carbonation and a more balanced tartness.

Essential Kombucha Ingredients and Ratios

Successfully brewing kombucha requires understanding the proper proportions of each ingredient. Our calculator automates these calculations, but knowing the science behind the ratios helps you troubleshoot and customize your brew.

Understanding Each Ingredient's Role

• Tea: Provides caffeine and tannins that feed the SCOBY. Black tea produces the most robust flavor, while green tea creates a lighter, more delicate kombucha. Avoid herbal teas containing oils (like Earl Grey or flavored teas) as these can damage your culture.
• Sugar: Plain white cane sugar is preferred because it ferments completely and cleanly. The SCOBY consumes most of the sugar during fermentation, so the finished kombucha contains significantly less sugar than the initial brew. Raw sugar, honey, or alternative sweeteners may produce inconsistent results.
• Starter Tea: This acidic liquid from a previous batch lowers the pH immediately, protecting against mold and harmful bacteria during the vulnerable early fermentation stage. Never skip the starter tea - it is essential for safe brewing.
• SCOBY: The living culture that transforms sweet tea into kombucha. A healthy SCOBY should be firm, cream-colored to tan, and smell mildly vinegary. It will grow a new layer with each batch.

The Science of Kombucha Fermentation

Understanding what happens during fermentation helps you produce consistently excellent kombucha. The SCOBY is a complex ecosystem containing multiple species of bacteria and yeast working together in a symbiotic relationship.

The yeast in your SCOBY, primarily Saccharomyces cerevisiae and Brettanomyces species, break down the sucrose (table sugar) into glucose and fructose. They then ferment these simple sugars into ethanol and carbon dioxide. Meanwhile, acetic acid bacteria (Acetobacter and Gluconobacter) convert the ethanol into acetic acid and gluconic acid - the compounds responsible for kombucha's characteristic tangy flavor.

This process also produces a variety of beneficial organic acids, B vitamins, enzymes, and polyphenols. The finished kombucha typically contains less than 0.5% alcohol (non-alcoholic by FDA standards), though this can vary based on fermentation conditions.

Scaling Your Kombucha Batch

Our calculator makes it easy to scale your kombucha recipe to any batch size. Whether you're brewing a small 1-quart batch to experiment with flavors or a large 5-gallon batch to stock your fridge for the month, the ratios remain consistent.

Second Fermentation and Flavoring Guide

The second fermentation, also called "2F," is where you add carbonation and create unique flavor combinations. After your first fermentation is complete, you bottle the kombucha with added fruit, juice, herbs, or spices and seal the bottles tightly. The remaining yeast continues fermenting, producing CO2 that carbonates your kombucha.

Popular Flavoring Combinations

• Ginger Lemon: 1 tablespoon fresh ginger + juice of 1/2 lemon per 16oz bottle. Creates a classic, zingy kombucha.
• Berry Blast: 2-3 tablespoons mashed berries (strawberry, blueberry, raspberry) per 16oz bottle. Produces beautiful color and natural sweetness.
• Tropical Paradise: 2 tablespoons mango or pineapple juice per 16oz bottle. Creates excellent carbonation and tropical notes.
• Lavender Honey: 1/2 teaspoon dried lavender + 1 teaspoon honey per 16oz bottle. Floral and soothing.
• Apple Cinnamon: 2 tablespoons apple juice + 1/4 teaspoon cinnamon per 16oz bottle. Perfect for fall.

Common Kombucha Problems and Solutions

Even experienced brewers occasionally encounter issues. Here are solutions to the most common kombucha problems:

Mold on SCOBY

True mold appears as fuzzy, circular spots - usually blue, green, black, or white - on top of the SCOBY. If you see mold, you must discard the entire batch including the SCOBY. Mold indicates your starter tea wasn't acidic enough or contamination occurred. Prevention: Always use adequate starter tea (10% of batch volume) and keep your brewing vessel and utensils scrupulously clean.

Vinegary or Too Sour

Over-fermented kombucha becomes increasingly vinegary. While still safe to drink, it may be unpleasantly sour. Use it as starter tea for your next batch or as a cleaning vinegar. To prevent: taste-test starting at day 7 and bottle when it reaches your preferred tartness.

No Carbonation

If your second fermentation produces flat kombucha, common causes include: bottles not sealed tightly, insufficient sugar for the yeast to ferment, or temperature too cold. Add a small amount of sugar or fruit juice, ensure bottles are properly sealed, and ferment at 75-80F.

SCOBY Sinks to Bottom

This is completely normal and not a problem. The SCOBY may float, sink, or turn sideways during fermentation. A new SCOBY will form on the surface regardless of where the mother SCOBY rests.