How to Lacto-Ferment Vegetables in Brine + Calculator

carrots in brine

Do you want to lacto-ferment vegetables but are unsure about how much salt to add to your brine? Then this is the tool and guide for you. 

How to use the brine calculator?

  1. Place your fermentation container on your digital scale and press tare/zero
  2. Fill the container with vegetables and cover completely with water
  3. Enter the total weight (vegetables + water).
  4. Select your brine % 
  5. Add the required amount of salt and mix well

What brine % should I use?

Generally you want to use around 2% of salt for harder vegetables (that have less water content) such as potatoes, carrots, beets. For softer vegetables a 3% of salt is suitable (more water weight) such as cucumbers, asparagus and mushrooms.

Baker’s percentage

This calculator uses the baker’s percentagemethod as a simple and accurate way of calculating the percentage of salt in your lacto-ferment. This means that we will add salt in relation to the weight of the vegetables and water we are fermenting and the total weight will exceed 100%. 

How do I prepare my vegetables for lactic-acid brine fermentation?

You want to look for the freshest and crispiest vegetables you can find to ferment. Old, mushy and soft vegetables do not ferment well. If you wouldn’t put the vegetables in your salad, then you better not ferment them. You don’t need to use organic vegetables, but if possible try to choose ones that are not heavily sprayed with pesticides since they can interfere with the fermentation process (many pesticides kill bacteria). A quick wash in water, or a light scrub to remove any dirt is all you need to do to prepare the veggies. 

Experiment with cutting the vegetables into different sizes and thickness based on your own preferences. 

How much water should I add to my lacto-ferment?

Add enough water to keep the vegetables fully submerged in water. If you are fermenting at a higher temperature add a bit more water to account for evaporation. 

Keep the vegetables covered with water at all times

It’s important to keep the vegetables fully submerged in water throughout the fermentation process to ensure a consistent result and to avoid mold growing on top. A lot of vegetables are excellent swimmers and will want to naturally float to the top, especially at the beginning of the fermentation so we will need to ensure they are kept under the water-line. 

Fermentation weights

These weights are designed to keep your ferments submerged under water. Made out of natural materials such as stone, clay or glass. Fermentation weights are great at keeping the vegetables under water. Just make sure to get weights that fit the container you are fermenting in. 

Vegetable leaves

When fermenting with leafy vegetables you can use the washed outer leaves of for example cabbage to keep the vegetables submerged under the brine. These leaves will not ferment properly and should not be eaten. 

Plastic bag filled with water

You can fill up a zip lock bag and use that as a weight to keep the vegetables submerged in the brine. Make sure to seal the bag well and if you can also double-bag it and add a teaspoon of salt if you are worried about the bag accidentally bursting or leaking. You can also add salt to the water in the bag so if it does break you just have some extra brine. 

Natural rocks and stones

Fermentation has been done for thousands of years and many home fermenters have found that using river rocks from fast flowing rivers are great to use as fermentation weights. Make sure you collect stones that are non porous and feel hard to the touch. Carefully wash the stones, scrubbing off any dirt, seaweed and carefully pouring boiling water over them to sanitise. If you are worried about contamination from the rocks put them into a plastic bag before using them as fermentation weights. 


For lactic acid fermentation with brine use a natural salt that easily dissolves in water. Avoid table salts that contain iodine since iodine has antibacterial properties that can negatively affect the lactic-acid bacteria we want to cultivate in our ferments. Fine sea salt is great for brines as it easily dissolves in water. You can certainly also use kosher salt to make the brine, but it’s harder to get it to dissolve and you might need to first dissolve the kosher salt in warm water and let it cool down before adding the brine to your ferment. 


The water you use can have an effect on your fermentation results and avoid using water directly from the tap as it contains chlorine that can kill the beneficial bacteria we need to ferment. There are many simple solutions to prepare your water for making brine.  

Use previously boiled water

If you have water that has been boiled you can use that for your brine. Or simply boil water and let it cool down to below 30°C (86°F) before adding it to your vegetables.

Use filtered water

Water filtered through active charcoal filters or reverse osmosis systems will remove the chlorine from water, so you can safely use it for your brine. 

Use day-old water or keep your water under sunlight

Chlorine evaporates from water, so if you have tap water that has been in a container for more than a day that will be safe to use for your brine. If you want to speed up the process you can also leave tap water out in direct sunlight for 30 minutes to remove the chlorine in the water. Remember not to put your ferments under direct sunlight as that will negatively affect the fermentation process and can also lead to the ferments overheating and killing the lactic acid bacteria which dies at temperatures over 71°C (160°F ). A glass container under strong sunlight can easily reach these high temperatures. 

What container should I use for my brine ferment?

You can use almost any non reactive container that will let your vegetables be completely submerged in the brine. Since the fermentation process will lower the pH and create a slightly acidic environment it’s best to use fermentation containers made out of glass, ceramics, or plastic (polycarbonate BPA free containers).

How do I add flavours and more complexity to my ferment?

Don’t be afraid to experiment with adding tasty vegetables to your lacto-ferments. The first time you ferment it’s usually a good idea to just ferment it with salt so you get an idea of what it tastes like fermented on its own. After that go crazy and experiment with all different kinds of flavours, that’s one of the most fun parts of fermenting. Popular aromatics include:

  • Garlic
  • Whole black pepper
  • Bay leaves
  • Mustard seeds
  • Cumin
  • Chillies (fresh or dried)
  • Thyme, Rosemary, Oregano

What temperature should I keep my brine ferment at?

Temperature plays an important part in almost every fermentation process. If it’s too cold it will take a long time for the fermentation process to get started and if it’s too hot it can result in undesirable flavours, textures and if it gets too hot the bacteria may even die. 

The optimal temperature for lactic acid ferments is usually between 25-32°C (77-90°F). To reach this you can keep it in a hot part of your kitchen, remembering to keep it out of direct sunlight. 

How long does it take to lacto-ferment vegetables in brine?

It depends on the flavour and consistency of what you like. The simple answer is that you can keep tasting your ferment after 1-2 days and then keep tasting it at regular intervals until it reaches the flavour that you like. When you do taste the ferments remember to use clean utensils or freshly washed hands to avoid contamination of the ferments. 

Keep a note of how long it took and what the temperature you fermented it at so you can recreate it again in the future. 

Keep in mind that depending on your climate it can take slightly longer to ferment in winter than in summer. 

Where should I store my fermented foods?

Find a place that keeps a slightly warm temperature in your house, and somewhere you can easily access the fermented foods so you can keep an eye on them and regularly do taste tests. Make sure to keep them out of direct sunlight. 

What should I do once the fermentation is finished?

Once the ferments have reached a desirable taste and consistency that you like, it’s time to eat some and enjoy the fruits of your fermentation and then store it.

Store the ferment at room temperature

You can safely keep storing the fermented foods at room temperature, however keep in mind that they will keep fermenting and may over-ferment or get overly acidic and sour. If you plan on eating the ferments within a few days or if you are interested in seeing how the flavour develops just keep it at room temperature and check back on it to see how it evolves. Remember to keep the vegetables submerged under the brine.

Store the ferment in the fridge or in a cold basement

A lower temperature will not stop the fermentation but it will significantly slow it down. So simply place your ferments in the fridge to slow down the fermentation process. It will keep at a similar taste for a longer period of time than if left out in room temperature. Remember to keep the vegetables submerged in brine though even if it’s in the fridge to avoid any mold or yeasts growing on the surface. 

How to freeze your finished ferments

If you freeze foods the fermentation process will stop. Freezing foods is like pressing a pause button and you can store the ferments indefinitely in the freezer and once you take them out they will maintain the same taste as when you froze them. While freezing will keep the flavours the same, the textures of certain ferments can be affected by the water crystallization when they freeze. For example crispy fermented cucumbers will lose their crispness after freezing. Freezing is a great way to keep your ferments for a longer period of time, in fact even Noma, one of the best restaurants in the world and grandmaster fermenters, are freezing some of their ferments.

Tips on freezing your lactic acid ferments

To successfully freeze your ferments it’s important to reduce the contact your ferments has with air as much as possible. You can do this by either vacuum packing the ferments prior to freezing. Or tightly wrapping the ferments with freezer plastic wrap and putting it into a freezer bag.

Common questions of lactic acid brine fermentation

Here are some of the most common questions when it comes to fermenting in brine. 

The brine is getting cloudy

This is a completely normal part of the process and nothing to worry about. 

The vegetables are not crispy enough

Remember to choose the freshest and best vegetables you can find to ferment and avoid fermenting slightly old or bruised veggies. If they are still getting soggy add a grape vine leaf, blackcurrant leaf or using a salt with more minerals inside such as Pink Himalayan Salt or Celtic Salt that can help the veggies stay more crispy. You can also try fermenting at a slightly lower temperature that can help the veggies stay more crispy. Adding more salt to your brine will also help keep the vegetables crisper as they will ferment slightly slower with a higher salt %. 

There is mold growing on the top of the brine

It’s fairly common for mold or kahms yeast to grow on top of your brine as you ferment. As long as the vegetables are still submerged, most experienced fermenters will simply scrape the mold from the top and keep the fermentation going and still eat it. 

Generally it’s best to use your senses and look, smell and touch the ferment to try and see if it’s gone off. A bad ferment will smell “off”, be slimy and generally unappealing. 

If you are worried about the safety of the foods or it feels scary, simply discard the ferment and start over again. 

It’s too salty

If you find the foods too salty after the fermentation process has finished you can place it into a bowl of unsalted water and the water and vegetables will attempt to reach equilibrium and osmosis will move some of the salt from the vegetables into the unsalted water. Keep in mind that you should eat the ferments after they have become less salty.. You can’t safely store the ferments after this process as the salt % may be too low.