Kombucha Brewing Ratio Calculator

How to Use This Tool

Enter your desired total kombucha batch size and select the unit (gallons, liters, or quarts). Choose your tea type (tea bags or loose leaf), preferred sweetness level, tea strength, and what percentage of the batch will be starter tea. Click Calculate Ratios to get precise ingredient measurements. Use the Reset button to clear all inputs and start over, or Copy Results to save the breakdown to your clipboard.

Formula and Logic

All calculations use US customary and metric conversion standards for accuracy:

• Batch volume is converted to liters for base calculations, then converted back to your selected unit for display.
• Starter tea volume is calculated as your selected percentage (10%, 15%, 20%) of the total batch volume.
• Water needed is total batch volume minus starter tea volume, as starter tea is added to cooled sweet tea.
• Sugar follows the standard ratio of 1 cup (200g) per gallon (3.785L) of water, adjusted by your sweetness multiplier (Low: 0.75x, Medium: 1x, High: 1.25x).
• Tea ratios use 2 tea bags (or 1 tbsp loose leaf) per gallon of water, adjusted by your tea strength multiplier (Light: 0.8x, Standard: 1x, Strong: 1.2x).

Practical Notes

Adjust these ratios for real-world home brewing scenarios:

• Use filtered, non-chlorinated water for best results, as chlorine can harm the SCOBY.
• Steep tea for 10-15 minutes for standard strength; longer steeping will increase bitterness, not tea flavor.
• Let sweet tea cool to room temperature before adding starter tea and SCOBY to avoid killing beneficial bacteria.
• First ferment typically takes 7-14 days; second ferment (with fruit/juice) adds carbonation and takes 2-3 days.
• Store finished kombucha in airtight bottles in the refrigerator to slow fermentation and preserve fizz.

Why This Tool Is Useful

Home kombucha brewing requires precise ratios to avoid over-sweetening, weak tea flavor, or mold growth. This tool eliminates guesswork for batches of any size, whether you’re making a single quart for personal use or a 5-gallon batch for a family. It adjusts for sweetness and tea strength preferences, so you can customize each batch to your taste without wasting ingredients.

Frequently Asked Questions

Can I use less starter tea than 10% of the batch?

Using less than 10% starter tea increases the risk of mold growth, as the starter tea lowers the pH to a level that inhibits harmful bacteria. Stick to 10-20% starter tea for safe fermentation.

Do I need to adjust ratios for second ferment?

This tool calculates first ferment ratios. For second ferment, use the finished first ferment liquid, add fruit or juice (about 10% of bottle volume), and seal tightly. No additional sugar or tea is needed for second ferment.

How do I convert loose leaf tea to tea bags?

1 standard tea bag is equivalent to 1 teaspoon of loose leaf tea. If using loose leaf, you can use a tea infuser or tie the leaves in cheesecloth to avoid floating debris in your batch.

Additional Guidance

Always use a glass container for brewing, as metal can react with the acidic kombucha. Keep your brew at room temperature (68-78°F / 20-25°C) away from direct sunlight. Save 2 cups of starter tea from each batch to use for your next brew, so you don’t need to buy starter repeatedly. If you notice mold (fuzzy blue, green, or black spots), discard the entire batch immediately, as it is unsafe to consume.