Kombucha Batch Size Calculator
How to Use This Tool
- Select Your Units: Choose between US Customary or Metric measurements.
- Input Your Vessel Size: Enter the absolute maximum volume of your brewing jar (e.g. 1 for a 1-gallon jar).
- Calculate Your Yield: The tool will automatically factor in the required safety headspace and scale your raw ingredients for a perfectly balanced batch.
Kombucha Batch Sheet
Fermentation ratios
Enter the maximum size of your jar. The calculator will automatically scale your ingredients to leave the required safe headspace.
You’ll need
Kombucha Vessel Capacity Cheat Sheet
Not all jars are filled equally. To maintain proper oxygen flow and liquid ratios, you can never fill a brewing vessel to the brim. Use this table as a quick reference for standard home brewing hardware.
| Vessel Size | Total Volume | Required Headspace Gap | Maximum Fluid Limit |
|---|---|---|---|
| Half Gallon Jar | 64 oz | 1.5 – 2 inches | ~54 oz |
| 1 Gallon Jar | 128 oz | 1.5 – 2 inches | ~114 oz |
| 2 Gallon Brewer | 256 oz | 2 – 3 inches | ~230 oz |
| 2.5 Gallon Brewer | 320 oz | 2 – 3 inches | ~288 oz |
The Baseline Math: How the Recipe Scales
When scaling a kombucha recipe, you cannot simply guess your liquid volumes. Unsweetened tea naturally sits at a neutral pH around 6.0 to 7.0. If you do not properly acidify this liquid before fermentation begins, your batch becomes highly vulnerable to wild mold.
To guarantee a safe chemical environment, this calculator utilizes a strict 12.5% starter liquid ratio.
While many generic recipes call for a loose 10% ratio, bumping this baseline to 12.5% ensures that the mature, highly acidic starter tea immediately drops the pH of your new batch to a safe level, regardless of minor fluctuations in your water source or tea strength. By calculating your exact jar volume and factoring in a safe headspace, this tool eliminates the guesswork and locks in a repeatable, mold-free primary fermentation every single time.