Fermentation Salinity Calculator – Online Kimchi & Sauerkraut Brine

Traditional Korean kimchi typically uses a 2–3% total salinity (based on total weight of vegetables + water). This range promotes Lactobacillus growth while inhibiting spoilage organisms. For a more sour, faster ferment, lean toward 2–2.5%. For longer storage (months), use 3%. Many home recipes call for a 3–5% brine solution when soaking cabbage, but after draining and mixing with other ingredients, the final salinity usually settles around 2–2.5%.

Different salts have dramatically different crystal sizes and shapes. Diamond Crystal Kosher Salt has large, hollow pyramid-shaped flakes — 1 teaspoon weighs only about 3.5g. In contrast, fine table salt has small, dense, cubic crystals — 1 teaspoon weighs about 6g. That's nearly double the weight for the same volume! If a recipe calls for "1 tablespoon of salt" without specifying the type, you could be off by 40–70%. Always weigh salt for the most accurate and consistent fermentation results. Use this calculator's salt type selector to get accurate volume estimates.

Brine salinity = salt ÷ water weight × 100% (used for brine-soaking methods). Total salinity = salt ÷ (water + vegetable weight) × 100% (used for overall ferment saltiness). For example, if you dissolve 30g of salt in 1L (1000g) of water, your brine salinity is 3%. But if you then add 1kg of cabbage, the total salinity drops to 30 ÷ 2000 = 1.5%. This distinction is crucial — many beginners make brine that's too weak because they forget vegetables dilute the salt. This calculator uses total salinity (water + vegetables) when vegetables are entered, giving a more accurate picture.

Generally not recommended. Salt concentrations below 1.5% may not sufficiently inhibit Clostridium botulinum, coliforms, molds, and other harmful microorganisms. While some experienced fermenters experiment with low-salt ferments (using starter cultures, airtight vessels, and strict hygiene), beginners should stay within the 1.5–5% safety window. The sweet spot for most lacto-fermented vegetables is 2–3% — enough to suppress pathogens while allowing beneficial lactic acid bacteria to thrive.

You can, but it's not ideal. Iodized table salt contains anti-caking agents (like calcium silicate) and iodine, which may slightly cloud your brine or subtly affect flavor. Some fermenters report that iodine can inhibit beneficial bacteria, though scientific evidence is mixed. For best results, use non-iodized fine sea salt, pickling salt, or kosher salt (check the label — some kosher salts contain anti-caking agents too). Himalayan pink salt and Celtic sea salt also work beautifully, though their mineral content may darken the brine slightly.

While a digital kitchen scale is highly recommended (they cost as little as $10–15), you can use volume measurements with caution. Use this calculator's salt type selector to get volume estimates matched to your specific salt. Key conversions for common salts:
• Fine Sea Salt: 1 tbsp ≈ 17g | 1 tsp ≈ 5.7g
• Diamond Crystal Kosher: 1 tbsp ≈ 10.5g | 1 tsp ≈ 3.5g
• Table Salt: 1 tbsp ≈ 18g | 1 tsp ≈ 6g
Remember: for the same "1 tablespoon," Diamond Crystal weighs nearly half as much as table salt. When in doubt, weigh it.

Yes! Reusing brine (back-slopping) can jumpstart fermentation by introducing active lactic acid bacteria. However, the salinity of used brine is depleted (salt was absorbed by the previous batch of vegetables). Do not rely on old brine's salinity — use this calculator to determine how much additional salt to add when reusing brine. A good rule of thumb: old brine has lost about 30–50% of its original salt content. Add fresh salt accordingly or treat the old brine as part of your water weight and calculate from scratch.