About

Fermentation is one of the few hobbies where the instructions regularly say things like “add honey until it feels right.” That’s fine for intuition. It’s less fine when you’re trying to scale a batch, troubleshoot a stuck ferment, or figure out why your starter has the consistency of wallpaper paste.

That’s the gap this site fills. Free calculators for the math that comes up over and over in sourdough, mead, kombucha, brine, and beyond. No account required. Nothing stored on a server. Just a number and an explanation of where it came from.

The tools

Sourdough — hydration, feeding ratios, bulk fermentation timing, levain builds, discard.

Mead — honey weight, ABV, nutrient additions (TOSNA and staggered), priming sugar, batch scaling, calories.

Kombucha — batch sizing, sugar ratios, second fermentation carbonation.

New tools get added when enough people ask for the same calculation. If you keep doing something by hand, let us know.

How it works

Every calculator runs in your browser. Nothing you type goes anywhere. The math is based on standard fermentation science and widely-used homebrewing formulas. Where there’s a real debate about methodology (nutrient timing in mead, for instance), we say so and let you pick.

Who it’s for

Home bakers, meadmakers, kombucha brewers, and anyone who has ever Googled “what is hydration percentage” at 11pm the night before a bake. Beginners welcome. Experienced fermenters who just want to stop doing arithmetic also welcome.