How to Can Tomatoes Safely: A Beginner Guide (2026)

The rule that keeps canned tomatoes safe: acidify every jar

Botulism spores survive boiling-water temperatures; the thing that stops them in a jar of tomatoes is acidity. A food is safe for water bath canning only if its pH is 4.6 or below, and tomatoes hover right around that line, close enough that you cannot trust an individual batch to be under it. So the tested recipes remove the guesswork by having you add a measured amount of acid to every jar.

This is not a flavor step you can skip if your tomatoes taste tart. Taste does not measure pH, and the amount of acid in the tested recipes is calibrated for safety, not seasoning. If the result is too tart for you, add a little sugar, but never cut the acid.

Experienced canners hammer the same point, especially at anyone who thinks a tart tomato is safe on its own:

You can process tomatoes in a water bath canner IF you use a modern recipe that calls for adding lemon juice. The acidity of tomatoes is not consistently safe without added lemon. Good luck!

I've been water bath canning diced tomatoes for decades, no problems. You must add bottled lemon juice, though. I water bath it forever, 85 minutes, and all I do is buzz the tomatoes in the food processor first. I don't even blanch them to remove the skins. Good luck with your endeavors!

Exactly how much acid, and which kind

Per the USDA and NCHFP, add to each jar before filling it:

• Quarts: 2 tablespoons of bottled lemon juice, or 1/2 teaspoon of citric acid.
• Pints: 1 tablespoon of bottled lemon juice, or 1/4 teaspoon of citric acid.
• Use BOTTLED lemon juice, not fresh: bottled has a standardized acidity, while a fresh lemon varies too much to rely on.
• Citric acid adds no flavor and is the choice if you do not want a lemony note; bottled lemon juice is easier to find.

Add the acid straight to the empty jar, then pack the tomatoes on top. Every jar, every time, whether they are whole, crushed, sauce, or juice.

If someone tells you the lemon juice is optional, they are wrong, and the correction is worth hearing plainly:

She said lemon juice didn't matter and I needed a pressure cooker. THANKS for letting me know i can do it if I'm using lemon juice !

Water bath or pressure canner?

Once acidified, tomatoes can be processed either way, and the choice is about convenience, not safety. A boiling water bath is the simpler entry point and the one most beginners use; our companion guide covers the best water bath canner for beginners. A pressure canner processes them faster and at a lower risk of siphoning, which is why some experienced canners prefer it, and it is the same pot you would use for low-acid foods later.

Either way, use the tested processing time for your exact product, jar size, and altitude, because a water bath boils cooler as you climb and the times assume you have adjusted. Do not improvise the time from another recipe.

Whole, crushed, sauce, or juice: match the recipe to the product

Tomatoes are canned in several forms, and each has its own tested recipe and time, so pick your product first and follow that recipe start to finish:

• Whole or halved (in water or juice): the simplest, and forgiving for a first batch.
• Crushed tomatoes: quick to make and endlessly useful for sauces and chili.
• Tomato sauce and juice: you run the tomatoes through a strainer or food mill to remove skins and seeds, which is where a dedicated tomato strainer earns its keep.
• Salsa and other mixes: only from a tested recipe, because added onions, peppers, and low-acid vegetables change the safety math.

For sauce and juice at any volume, a food strainer or sauce maker separates skins and seeds far faster than a food mill and a strainer by hand.

Your first batch of canned tomatoes, step by step

Start with whole or crushed tomatoes in a water bath. Then:

• Wash jars, bands, and lids. Blanch the tomatoes 30-60 seconds in boiling water, drop them in ice water, and the skins slip right off.
• Add the acid (bottled lemon juice or citric acid) to each empty jar first.
• Pack the tomatoes in, hot or raw per your recipe, leaving 1/2 inch headspace. Add hot water or juice if the recipe calls for it.
• Slide a bubble tool around the inside to release trapped air, wipe the rims clean, set flat lids on, and thread bands to fingertip-tight.
• Lower jars onto the rack, cover by 1-2 inches of water, bring to a full boil, and start timing the recipe time for your altitude.
• When time is up, turn off the heat, wait 5 minutes, lift the jars onto a towel, and leave them undisturbed 12-24 hours.

The next day, check that each lid is sealed (concave, does not flex). Refrigerate any that did not seal and use them soon. Label the rest with the date.

First-time nerves are normal, and they fade fast:

These look great! We also canned for this first time this weekend, some yummy salsa! It’s scary (I am paranoid about the safety aspect too) but I think it’s something that becomes less scary with practice.

The tomato-canning mistakes that are actually dangerous

• Skipping the acid because the tomatoes taste tart. Taste is not pH; add the measured acid every time.
• Using fresh lemon juice instead of bottled. Fresh acidity varies too much to be safe.
• Canning tomatoes from dead, frost-killed, or diseased vines, which can be too low in acid; NCHFP says do not can those.
• Water bath canning a low-acid mix (salsa or sauce with lots of added onion and pepper) from an untested recipe. Use a tested salsa recipe or pressure can it.
• Following a "grandma" or blog recipe with no acid and an oven or open-kettle method. Use a current tested recipe from NCHFP, USDA, or the Ball Blue Book.

Why the tested-recipe rule is not negotiable, put plainly by the people who have watched others learn it the hard way:

because there is no tested recipe for it. and we can't just assume using another method or adding more acid is sufficient for safety.

So what should you buy?

For a first tomato season you need a water bath canner and rack, standard Mason jars, and a bottle of lemon juice or a jar of citric acid from the grocery store. If you want sauce or juice without hand-peeling bushels of tomatoes, add a tomato strainer. The picks below cover the setup; the acid itself is a cheap grocery-aisle buy.