What a salt percentage means in a vegetable ferment
A fermentation salt percentage is a mass fraction: grams of salt per 100 grams of the thing you are salting. It is written % w/w and it has nothing to do with volume, cups, or the size of the jar. When a sauerkraut recipe says 2%, it means 20 g of salt for every kilogram of shredded cabbage — and it means that whether your cabbage is dense winter white or loose savoy, because you are weighing, not filling.
Salt does three jobs at once here, and each one wants a slightly different dose. It draws water and soluble sugars out of the vegetable cells by osmosis, which creates the liquid the ferment lives in. It suppresses the organisms that would otherwise get there first — most spoilage yeasts, moulds, and pseudomonads tolerate salt poorly, while Leuconostoc and Lactobacillus tolerate several percent comfortably. And it keeps pectin firm, so the pickle stays crisp instead of collapsing.
That salt-tolerance gap is the whole mechanism. You are not sterilising anything. You are tilting a competition that the lactic acid bacteria then win on their own by producing acid, and once the pH drops below about 4.0 the acid takes over the protective role from the salt. The percentage you choose decides how wide the head start is and how fast the ferment runs.
Three ways to apply the percentage, and why they give different answers
The arithmetic is one multiplication. The judgement is deciding what you multiply. Recipes are careless about this, which is why two sources can both say "2% salt" and mean quite different jars.
Dry salting applies the percentage to the vegetable weight alone. You shred, weigh, scatter the salt, and massage until the vegetable releases enough liquid to submerge itself. Sauerkraut and most kimchi work this way. No water is added, so the equilibrium salinity of the finished jar equals your target exactly.
A covering brine applies the percentage to the water alone. You mix, say, a 3.5% brine and pour it over whole cucumbers or beans. This is the traditional method for anything too dense to release its own liquid. The catch is that the vegetables are mostly unsalted water themselves, so within a day or two the salt redistributes and the whole jar sits well below the strength you mixed. A 3.5% brine over an equal weight of cucumbers ends up near 1.75%.
An equilibrium brine applies the percentage to everything in the jar — vegetables plus water — so the number you enter is the number the ferment actually experiences once diffusion finishes. It takes one extra weighing and it is the only method of the three where the target and the outcome are the same number by construction. If you want repeatability across different vegetables and different jar packings, use this one.
The calculator shows you the equilibrium salinity for all three, so you can enter a traditional covering-brine recipe and immediately see what it is really doing.
Worked example: 1,800 g of cabbage at 2%, then the same batch as a covering brine
You have trimmed and shredded a large head of cabbage. The scale reads 1,800 g. You want a standard 2% kraut, and you own Diamond Crystal kosher salt at about 2.8 g per teaspoon.
- Pick the reference weight. Dry salting, so Wref = 1,800 g of cabbage.
- Multiply. 1,800 × 2 ÷ 100 = 36 g of salt.
- Convert to volume if you must. 36 ÷ 2.8 = 12.9 teaspoons, which is 4.3 tablespoons. With Morton coarse kosher at 4.8 g/tsp the same 36 g is only 7.5 teaspoons — the identical weight, nearly half the volume. This is why weight wins.
- Check the equilibrium. No water added, so total contents = 1,800 g and salinity = 36 ÷ 1,800 × 100 = 2.00%.
Now suppose the cabbage is coarse-cut and refuses to release enough liquid, so you top the jar up with 400 g of water. Recompute honestly: the salt is still 36 g but the contents are now 2,200 g, so the ferment sits at 36 ÷ 2,200 × 100 = 1.64%. To hold 2.00% you would need 2,200 × 0.02 = 44 g of salt — the extra 8 g being exactly 2% of the 400 g of water you added. Switch the method selector to equilibrium and the calculator does this for you.
The covering-brine route on the same jar looks different again. Mix 400 g of water at 3.5% and you add 14 g of salt; the jar then holds 14 g in 2,200 g, or 0.64% — far too weak for cabbage. Covering brines are for vegetables you are packing whole, where the water makes up half the jar or more.
How to read the result and choose a percentage
Read the equilibrium salinity figure, not your target. That is the number the bacteria see, and it is the one to compare against any published range.
Between roughly 1.5% and 3% is where most vegetable ferments live. At the low end fermentation is fast and the flavour is bright but the margin for error is thin: any vegetable that floats above the liquid will grow mould, and warm rooms push the batch towards yeasty, softening outcomes. At the high end the ferment slows, stays crisp for months, and tastes distinctly salty — appropriate for something you will rinse or use as a condiment.
Temperature works alongside salt rather than independently of it. Warmth speeds every organism in the jar, but it speeds the yeasts and the softening organisms more than it helps you, which is why summer kraut is more prone to going soft and yeasty than winter kraut at the identical percentage. Cool storage and a higher salt percentage both narrow the same problem, so the practical move when your kitchen is warm is to nudge the salt up within the 1.5–3% band and to check the jar more often — not to invent a conversion between degrees and percentage points, because no published equivalence exists.
Above about 5% you have left ordinary vegetable fermentation and entered the territory of salt-tolerant organisms: brined olives, salted lemons, miso and soy mashes. Those ferment over months, not days, and the calculator will flag it.
One thing salt percentage does not fix is submersion. Salt protects liquid; it does nothing for a shred of cabbage floating in the air gap. Weight the vegetables under the brine with a glass weight or a brine-filled bag before you worry about a tenth of a percent of salt.
Typical salt percentages by ferment
| Ferment | Usual method | Equilibrium salinity | Salt per 1,000 g of contents |
|---|---|---|---|
| Sauerkraut | Dry salt | 1.8–2.5% | 18–25 g |
| Kimchi (after the cabbage is rinsed) | Dry salt, then rinse and season | 1.5–3.0% | 15–30 g |
| Fermented cucumber pickles | Covering brine | 2.0–3.5% | 20–35 g |
| Fermented hot sauce mash | Dry salt or equilibrium | 2.0–3.0% | 20–30 g |
| Green beans, carrots, radish | Covering brine | 2.0–3.0% | 20–30 g |
| Brined olives, preserved lemons | Covering brine | 5–10% | 50–100 g |
Ranges are working practice, not a standard. Any percentage in the table is a starting point to be adjusted for your temperature and your taste.
Mistakes that change the salinity without you noticing
- Measuring salt by volume across brands. A teaspoon of Diamond Crystal is about 2.8 g and a teaspoon of fine table salt about 6.0 g. Swapping brands at the same teaspoon count changes the dose by more than a factor of two.
- Using iodised salt or salt with anti-caking agents. Iodine inhibits some lactic acid bacteria and anti-caking agents cloud the brine. Pickling, kosher and pure sea salt are all fine; read the ingredients rather than the name on the front.
- Weighing the cabbage before trimming. Core and outer leaves you discard are not in the jar. Weigh what goes in, after cutting.
- Topping up with unsalted water mid-ferment. Every gram of plain water added dilutes the salinity. Top up with brine mixed to the same equilibrium percentage instead.
- Quoting a covering-brine percentage as if it were the jar salinity. A 5% brine over a densely packed jar can equalise near 2%. Read the equilibrium figure.
- Assuming salt makes the batch safe. Salt buys time for acidification. Acidity is what preserves the finished product, and a ferment that never drops below pH 4.6 has not been preserved by anything.
Fermenting is not canning
A fermented vegetable is preserved by acid produced in the jar, and it is stored cold. It is not shelf-stable because it was salted. If you want to move a finished ferment to the pantry you must process it in a boiling-water bath, which stops the fermentation and softens the texture — and you then need a tested processing time and the altitude adjustment for your elevation. Sodium nitrite curing salts have no place in a vegetable ferment; they belong in meat, where the ingoing nitrite calculation is a regulated quantity.
Where this sits among the other salt calculations
Percentage-by-weight salting is one idea used across several very different processes, and it is worth knowing which one you are in.
In dry brining meat the percentage is applied to the meat and the salt is meant to be fully absorbed, so 1% means the finished steak is 1% salt. Nothing ferments; you are seasoning and altering protein structure.
In sausage making salt is dosed at 1.5–2% of the meat block for the specific purpose of solubilising myosin so the emulsion binds, and it sits alongside a separately calculated cure.
In kombucha there is no salt at all — the equivalent protective step is the acidic starter liquid, dosed at 10–20% of the batch, which drops the pH immediately rather than waiting for salt to hold the line.
What all of these share is the discipline of the baker's-percentage mindset: express every ingredient as a fraction of one reference weight, and the recipe scales to any batch size without arithmetic errors. Write your ferments down as percentages and a scale is the only equipment you need to reproduce them.
For safety questions beyond the fermentation itself — botulism risk in oil-packed or low-acid preparations, and the acidification requirements for shelf storage — the National Center for Home Food Preservation and the USDA guides listed below are the authorities to follow, not a recipe blog.