Getting the salt right is the difference between crisp, tangy ferments and a spoiled jar. This fermentation brine calculator works out exactly how much salt you need for any batch, whether you are making a submerged brine for pickles or salting shredded cabbage for sauerkraut. Set your water or vegetable weight, pick a salt strength, and it does the maths in grams and spoons.
Fermentation Brine Calculator
Use non-iodised salt (sea, pickling or kosher) and non-chlorinated water, and keep everything under the brine. Values are a starting point, adjust to taste. Coarse or kosher salt weighs less per spoon, so weigh it when you can.
How much salt should I use?
There are two ways to salt a ferment, and the calculator covers both:
- Brine (submerged vegetables) - for whole or chunky veg kept under liquid, like cucumbers, cabbage leaves or radishes. Salt is a percentage of the water weight. One litre of water weighs 1000 g, so a 5% brine is 50 g of salt.
- Salt by weight (kraut and kimchi) - for shredded or mashed veg that makes its own brine, like sauerkraut or kimchi. Salt is a percentage of the vegetable weight, usually 2 to 2.5%.
- Dill pickles (ogorki kiszone): a 3% brine, which is 60 g of salt to 2 litres of water. Try my Polish fermented dill pickles.
- Sauerkraut: 2% salt by cabbage weight. If yours stays mild, here is why sauerkraut is not sour and what to change.
- Kimchi: 2% salt by vegetable weight, not a brine. Salt the vegetables, rinse them, then season. See my cucumber kimchi and vacuum-bag kimchi method.
- Beetroot kvass: a 5% brine, which is 20 g of salt to 400 ml of water. Here is my beetroot kvass.
Which vegetables ferment well
Almost any firm vegetable will ferment, but they do not all want the same amount of salt and they do not all come out of the jar the same. This is what to expect from the ones worth doing, and what to do with each one before it goes in.
| Vegetable | Salt | Before it goes in | How it comes out |
|---|---|---|---|
| Cucumbers | 3% brine | Small, firm, thin-skinned pickling varieties, picked before the seeds soften. Trim the flower end off every one. | Crisp, if you keep them under the brine and add tannin leaves. |
| Cabbage, finely shredded | 2% of the cabbage weight, dry-salted | Shred it as thin as you can and work the salt in until it gives up its own liquid. No added water. | Tart and aromatic, and softer the longer it goes. |
| Cabbage and radish, in pieces | 2% of the vegetable weight, dry-salted | Cut into pieces rather than shredded, salt, then rinse before the paste goes on. | Crunchy, and less sour than sauerkraut because it ferments cold. |
| Radish, mooli or daikon on its own | 3 to 4% brine | Thick batons or rounds. Thin slices go floppy. | The crispest thing in this table. |
| Carrots | 2 to 3% brine | Sticks, or coarsely grated if you want it ready in days rather than weeks. | Stays firm. Grated goes soft faster. |
| Beetroot | 5% brine | Peeled and sliced or cut into chunks. Do not grate it: too much sugar at once and it goes slimy. | The beetroot stays firm, but the liquid is the point. |
| Aubergine | 4 to 10% brine | Small ones whole or halved, salted heavily. This is a Japanese pickle rather than a European one. | Soft, deeply savoury, strongly salted. |
| Mixed vegetables | 3.5% brine | Cut everything to roughly the same size so it ferments at the same rate. | Depends on what is in it. Keep the soft things out. |
The mixed vegetables row is the one I use for my fermented radish, carrot and beetroot, a 3.5% jar.
My own two are at the gentle end on purpose. Published pickle recipes usually cure cucumbers in a 5 to 8% brine and published kimchi runs at 3 to 4%, where mine sit at 3% and 2%. Less salt ferments faster and tastes less aggressively salty, and the trade is a smaller margin for error: keep everything under the liquid and do not let the jar get warm.
What actually keeps them crisp
Three things, and none of them is the amount of salt.
- Use unrefined salt. Rock salt and unrefined sea salt carry small amounts of calcium and magnesium, and those cross-link the pectins in the cell walls. That is the difference between a firm pickle and a bendy one, and it is why the calculator warns you off table salt.
- Trim the flower end off cucumbers. The remains of the flower at the far end from the stalk carry microbes whose enzymes soften the fruit from the inside. Cut a few millimetres off and the problem goes with it. This is the single most useful thing on this page if you have ever had a jar of mushy pickles.
- Add tannin. Oak, blackcurrant, grapevine or cherry leaves, or a piece of horseradish root, all go into my Polish fermented dill pickles for this reason.
And one thing that undoes all three: air. Anything floating above the brine grows a film of yeasts and moulds that eat the acid you have just made, and softening and off smells follow. Weigh the vegetables down.
The ones to pickle in vinegar instead
Green beans, okra, pumpkin, mushrooms, watermelon rind, pears and peaches are nearly always pickled in vinegar rather than fermented, at around 2.5% acetic acid, which is standard vinegar cut by half. It is faster, it gives you more control over the texture, and the flavour is simpler for it. Carrots go either way. If you want one of those in a jar this week, the calculator is the wrong tool: you want vinegar, not brine.
Tips for a safe ferment
- Stay at 2% salt or higher. Below that, spoilage bacteria can get ahead of the good lactic acid bacteria.
- Use non-iodised salt (sea salt, pickling salt or kosher salt). Anti-caking agents can cloud the brine. Iodised salt works, but plain salt is what I use.
- Use non-chlorinated water. If your tap water is treated with chlorine, a night on the counter or boiling it and letting it cool gets rid of it. If it is treated with chloramine, as a lot of US water is, neither works, so use bottled water or ask your water supplier which one they use.
- Make the brine cold. I just stir the salt into cold water for a few minutes until it disappears. If you are in a hurry, warm a small part of the water, dissolve the salt in that and top up with the rest cold. Never pour warm brine over the vegetables: the bacteria that do the fermenting live on the vegetables themselves, and heat kills them and softens the veg.
- Keep everything under the brine with a weight. Anything above the surface can grow mould.
What You’ll Need for Fermenting
A handful of basics make fermenting simple and safe. These are the tools I actually reach for in my own kitchen.
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FAQ
What percentage of salt do I need to ferment vegetables?
Most vegetable ferments sit between 2% and 5%. Shredded ferments like sauerkraut and kimchi use about 2 to 2.5% of the vegetable weight, while submerged pickles use a 3 to 5% brine. Staying at 2% or above keeps the ferment safe while the good bacteria take over.
Should I measure salt by weight or by spoons?
By weight whenever you can. A tablespoon of fine sea salt weighs far more than a tablespoon of flaky or coarse kosher salt, so spoons are only a rough guide. The calculator shows grams first and gives an approximate spoon count for fine sea salt.
Can I make my ferment less salty?
You can go as low as 2% for a milder result, but do not go under it for long ferments. If you want less salty pickles, ferment a little faster in a warmer spot and move the jar to the fridge as soon as they taste right.