Tools in This Collection
Sourdough Calculator
Scale sourdough recipes by desired dough weight
Sourdough Hydration Calculator
Calculate baker's percentages and hydration levels
Kimchi Calculator
Scale kimchi ingredients by cabbage weight
Sauerkraut Calculator
Calculate salt-to-cabbage ratio for fermentation
Kombucha Calculator
Scale tea, sugar, and SCOBY for kombucha batches
Water Kefir Calculator
Calculate sugar water ratios for water kefir grains
Fermentation Temperature Guide
Optimal temperature ranges for fermented foods
Brine Calculator
Calculate salt brine percentages for meat and vegetables
Pickling Brine Ratio
Calculate vinegar-to-water ratios for quick pickles
Guides & Articles
The Science of Fermentation: Getting the Numbers Right
Fermentation is one area of cooking where getting the numbers wrong has real consequences — under-salted vegetables can spoil rather than ferment safely, and over-salted results in unpalatably salty food. Salt ratios are the foundation of lacto-fermentation: sauerkraut uses 2-3% salt by cabbage weight, kimchi uses 2.5-3.5%. The Sauerkraut Calculator and Kimchi Calculator handle this by weight, not volume — because a tablespoon of fine salt weighs significantly more than a tablespoon of flaky sea salt.
Sourdough Hydration and Starter Management
Sourdough hydration (the ratio of water to flour) determines crumb structure and handling. Beginners do well at 65-75% hydration — the dough is manageable and forgiving. Open crumb enthusiasts push to 80-85%+, which requires stronger gluten development techniques. The Sourdough Hydration Calculator calculates baker's percentages for any recipe, and the Sourdough Calculator scales full recipes by desired dough weight — so you can plan batches that fit your banneton, Dutch oven, or loaf pan exactly.
Kombucha, Water Kefir, and Brine
Kombucha fermentation requires 1 cup (200g) of sugar per gallon of tea to feed the SCOBY culture. The Kombucha Calculator scales tea, sugar, and SCOBY ratios for any batch from 1 quart to 5 gallons. Water kefir grains need 3-4 tablespoons of sugar per quart — the Water Kefir Calculator scales for any jar size. For brining meat and vegetables, the Brine Calculator handles both percentage-based brining (weight of salt vs. weight of water) and the quick-reference brining guide is available at Guide to Brining Meat. Quick pickles use a different approach: 1:1 vinegar-to-water ratio (sometimes 3:2 for more acidity) with 1 Tbsp salt per cup of liquid. The Pickling Brine Ratio Calculator scales vinegar, water, and salt for any jar size.
Fermentation Temperature
Temperature is the other critical variable. Sourdough ferments fastest at 76-80°F (24-27°C). At 65°F (18°C), bulk fermentation takes 2x as long, developing more sour flavor. Kimchi at room temperature (70°F) ferments in 1-2 days; in the refrigerator, the same batch takes 1-2 weeks. The Fermentation Temperature Guide shows optimal ranges for different ferments and explains how temperature shifts change timing and flavor profile.
Frequently Asked Questions
Is lacto-fermented food safe to eat?
Yes, when salt percentages are correct. Lacto-fermentation creates an acidic, anaerobic environment that prevents the growth of harmful bacteria. The key is using enough salt (2-3% by vegetable weight) and keeping vegetables submerged below the brine. Mold on the surface is a sign of air exposure — not spoilage — and can be scraped off if the brine below smells sour and not putrid.
What salt percentage should I use for fermentation?
For sauerkraut and kimchi: 2-3% salt by weight of vegetables (20-30g salt per 1000g cabbage). For brine solutions used with cucumbers and other whole vegetables: 2-5% salt by weight of water. Measure by weight, not volume — different salts have very different densities, making volume measurements unreliable.
What hydration level should a beginner sourdough baker use?
Start at 65-70% hydration. At this level the dough is manageable, less sticky, and still produces excellent bread. Once you're comfortable with shaping and reading fermentation, push to 75-80% for more open crumb. Hydration above 80% requires strong gluten development and is harder to shape without the dough spreading.
How long does kombucha take to ferment?
Primary fermentation (first ferment) takes 7-14 days at room temperature (68-78°F). A longer ferment produces more vinegary, less sweet kombucha. Secondary fermentation in bottles (for carbonation) takes 2-4 days at room temperature, then refrigerate. Taste your primary ferment at day 7 — if it's still very sweet, leave it longer.