Free Tool
Fermentation Yield Predictor
Enter your vegetable and fresh weight. Get exact jar count, brine volume, salt needed, and final fermented yield before you start packing.
Jars needed
—
enter weight
Salt
—
grams
Brine water
—
ml
Final yield
—
oz
Final yield
—
cups
Weight loss
20%
typical
Peak flavor
14
days at 70°F
Why fermenting vegetables shrink
When vegetables ferment, lactic acid bacteria break down cell walls and osmotic pressure draws water out of plant tissue. Salt accelerates this by pulling intracellular liquid through osmosis — which is why sauerkraut releases so much brine without adding any water at all. As fermentation progresses, cell structures collapse further, and what started as a tight pack of crisp vegetables becomes softer and more compact. The liquid released becomes part of your final brine volume, carrying probiotics and flavor compounds along with it. Mushrooms shrink the most (up to 40%) because they have high water content and thin cell walls. Carrots shrink the least (around 10%) because dense, fibrous tissue holds its structure through fermentation.
The shrinkage percentage in the calculator is the approximate volume and weight reduction you can expect from the vegetable solids alone. Brine volume stays relatively stable — it absorbs some vegetable liquid but does not disappear. Your final yield in cups or ounces is calculated from both the shrunken vegetable mass and the total brine in the jar.
Yield by vegetable type
Frequently asked questions
How much sauerkraut does 1 head of cabbage make?
A medium head of cabbage weighs around 900g to 1,200g. After shredding and removing the outer leaves, you are working with roughly 700 to 900g of usable cabbage. At 20% shrinkage, a 900g head of cabbage produces about 720g of finished sauerkraut, which is roughly 3 cups. One head of cabbage typically fills one 32oz jar.
Why do my fermented cucumbers shrink so much?
Cucumbers are 96% water by weight, and brine fermentation draws out that moisture through osmosis while softening the cell walls. The salt concentration, temperature, and fermentation time all affect final texture. For crunchier pickles, use 3 to 5% brine, add a grape leaf or horseradish leaf for tannins, and ferment at cooler temperatures around 60 to 65 degrees F. The 15% shrinkage estimate here is a baseline and your results may vary.
Should I pack jars completely full?
No. Leave at least 1 inch of headspace below the lid. During active fermentation, CO2 production causes the brine to bubble and expand. A jar packed too tightly will overflow and potentially blow the lid. For submerging vegetables below the brine line, use a fermentation weight or a zip-lock bag filled with brine. The calculator above accounts for headspace by using the total jar volume as packing capacity.
How long does fermented food last in the fridge?
Properly fermented vegetables stored in the fridge last 3 to 6 months for most vegetables, and up to 12 months for lower-moisture ferments like garlic or hot sauce. The key is keeping vegetables submerged below the brine line because exposure to air promotes mold. A pH below 4.4 is considered safe from pathogen growth. If you have a pH meter, target 3.5 to 4.0 for long-term storage.
Can I refill the brine if it evaporates?
Yes. Mix a fresh batch of brine at the same salt percentage you used originally and top off the jar to keep vegetables submerged. Never top off with plain water because it dilutes the salt concentration and can create conditions for spoilage. Keep a small jar of reserve brine in the fridge whenever you start a new ferment.