Fermentation Calculator — Drink Theory Studio

Choose what you're fermenting, fill in your batch details, and calculate. This is a working guideline from studio field practice, not a lab-calibrated or food-safety instrument — always taste, smell, and look before you trust a number here. Once a wine or kombucha batch is bottled, the Shelf Life & Storage Calculator can help you think about how long it keeps.

Field notes

Salt percentage is the real control

Everything else about a vegetable ferment — texture, speed, safety margin — follows from getting the salt percentage right. Too little and spoilage organisms can outcompete the lactic acid bacteria you want; too much and fermentation slows to a crawl. The ranges here are a starting point, not a guarantee.

Kombucha strength is a trade, not a target

A longer first ferment trades sweetness for tartness and, eventually, acidity that can taste more like vinegar than tea. There's no universally "correct" F1 length — only the point where it tastes right to you, which this tool can only estimate toward.

A hydrometer beats a guess, every time

Potential ABV, sugar additions, and dry vs sweet finishes all depend on an actual starting gravity reading. Fruit type, ripeness, and growing conditions vary far too much for any tool to estimate sugar content from a fruit name alone.

Grains are alive, not an ingredient

Kefir grains grow, get sluggish in the cold, and speed up in the warmth — the amount and timing here are a starting point for one batch, not a fixed recipe. Watch how your particular grains behave and adjust from there.

What this tool cannot know

It has no idea what's actually happening in your jar today. This is a working guideline from studio field practice, not a food-safety, toxicology, or laboratory instrument — trust your taste, smell, and eyes over any number here, and when in real doubt, discard the batch.

This tool offers a starting structure from studio field practice — it is not a food-safety, toxicology, or laboratory instrument. Keep vegetable ferments fully submerged; discard anything with fuzzy mould, an "off" smell, or unexpected colour rather than a normal sour one. A hydrometer is the only reliable way to know a wine must's actual starting gravity. When in doubt, throw it out.