All home-canned tomatoes need added acid to be safe, because modern tomatoes are borderline low-acid. Enter your jar size, how many jars, and your acid of choice, and this calculator gives the amount to add per jar and in total, using the standard tested rates for plain whole, crushed, or juiced tomatoes and plain tomato sauce.
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What Your Result Means: the per-jar amount is what to add to each jar before filling and processing. The total is simply that amount times your number of jars, so you can measure it all out at once.
How Much Acid for Canning Tomatoes?
The tested rate per quart is 2 tablespoons of bottled lemon juice, 1/2 teaspoon of citric acid, or 4 tablespoons of 5% vinegar. Pints take half those amounts. Enter your jars and acid, and the tool totals it for the whole batch.
- Enter the Jars, how many and their size.
- Choose the Acid, bottled lemon juice, citric acid, or vinegar.
- Read the Amounts, per jar and the batch total.
What Each Result Means
| Result | What It Tells You |
|---|---|
| Per jar | Add this to each jar before filling |
| Batch total | Amount for all your jars together |
| Acid type | The tested product you selected |
Acid Rates per Jar
Standard tested amounts to acidify home-canned tomatoes and tomato products.
| Acid | Per Pint | Per Quart |
|---|---|---|
| Bottled lemon juice | 1 tablespoon | 2 tablespoons |
| Citric acid | 1/4 teaspoon | 1/2 teaspoon |
| Vinegar (5%) | 2 tablespoons | 4 tablespoons |
How Is the Amount Worked Out?
Each acid has a fixed amount per jar size. The tool multiplies that per-jar amount by your number of jars, then converts large totals into cups or tablespoons so they are easy to measure.
Per pint: half the quart amount
Batch total = per-jar amount x number of jars
Quarts get twice the pint amount because they hold twice as much. Always add the acid to the jar, then fill and process as your tested recipe directs.
Worked Example
Say you are canning 7 quarts of crushed tomatoes with bottled lemon juice. Each quart takes 2 tablespoons, so you add 2 tablespoons per jar and need 14 tablespoons total, which is a little under one cup. Sugar or salt for flavor is optional, but the acid is not.
Which Acid Should You Choose?
- Bottled lemon juice: easy to find and reliable; adds a mild lemon note.
- Citric acid: tiny amounts, no added liquid, and the most neutral flavor.
- Vinegar (5%): works but takes twice the volume of lemon juice and may cause undesirable flavor changes.
- Never fresh lemons: their acidity varies, so they are not safe for canning.
- Sugar can balance flavor: add a little if the acid makes the tomatoes taste tart, without changing the acid amount.
Understanding Your Outputs
| Output | Meaning | Best Used For |
|---|---|---|
| Per jar | Add before filling | Acidifying each jar |
| Batch total | All jars together | Measuring in one go |
| Acid type | Product selected | Shopping and labeling |
When to Use It
Use it when you can plain whole, crushed, or juiced tomatoes or plain tomato sauce, in a water-bath or pressure canner. Do not use it for salsa, tomato paste, or mixed-vegetable recipes: those tested recipes build the acid into the batch, so use exactly the acid the recipe lists. Pair it with the canning yield calculator for how many jars.
Common Mistakes to Avoid
- Skipping the acid: modern tomatoes are borderline low-acid, so every jar of plain tomatoes, juice, or sauce needs it.
- Using fresh lemon juice: its acidity varies and is not safe; use bottled.
- Halving the acid to reduce tartness: add a little sugar instead, never less acid.
- Forgetting a jar: measure the total but still add the correct amount to each jar.
- Ignoring the recipe: acid is one step; follow a tested recipe and process time.
Accuracy and Limitations
The rates here are the standard tested amounts for home canning of tomatoes.
What It Calculates: the acid to add per jar and for the batch.
What It Does Not Replace: a complete tested recipe and the correct processing method and time. Follow the National Center for Home Food Preservation or your canner’s guide for the full process.
Methodology
Method: the calculator uses the standard tested acidification rates and multiplies the per-jar amount by the number of jars. Rates: per quart, 2 tablespoons bottled lemon juice, or 1/2 teaspoon citric acid, or 4 tablespoons 5% vinegar; pints take half. Inputs Used: number of jars, jar size, and acid type. Conversions: 16 tablespoons per cup and 3 teaspoons per tablespoon for readable totals. Note: acid is required for safety and does not replace a tested recipe or the correct process time. These per-jar rates are for plain tomatoes, juice, and sauce only; salsa, paste, and mixed-vegetable recipes use the acid their tested recipe specifies.
Sources: National Center for Home Food Preservation – Canning Tomatoes, Healthy Canning – Acidifying Tomatoes, NCHFP – Tomato Acidification Directions. Last reviewed: September 26, 2026 · Reviewed by Aiza Anwar.
Frequently Asked Questions
How much lemon juice do I add to canned tomatoes?
Add 2 tablespoons of bottled lemon juice per quart, or 1 tablespoon per pint, to every jar of plain home-canned tomatoes, juice, or sauce before filling and processing. Salsa and paste use the acid their tested recipe specifies.
How much citric acid per quart of tomatoes?
Use 1/2 teaspoon of citric acid per quart, or 1/4 teaspoon per pint. Citric acid adds no liquid and has the most neutral flavor.
Can I use fresh lemon juice instead of bottled?
No. Fresh lemon juice varies in acidity, so it is not safe for canning. Use bottled lemon juice, which has a standardized acid level.
Why do I need to add acid to tomatoes at all?
Modern tomato varieties sit near the safety line between acid and low-acid foods. Added acid guarantees the jars are acidic enough to can safely.
Does adding acid change the flavor?
A little. If the tomatoes taste too tart, add a small amount of sugar to balance it. Never reduce the acid to soften the flavor.
Can I use vinegar to acidify tomatoes?
Yes, 5% vinegar works at 4 tablespoons per quart, but it takes twice the volume of lemon juice and may cause undesirable flavor changes, so many people prefer lemon juice or citric acid. Never use vinegar in place of lemon juice in a salsa recipe.
Do I still add acid if I pressure can tomatoes?
Yes. Acidification is recommended for tomatoes whether you use a water-bath or a pressure canner, because it is about the food’s acidity, not the method.
Where do I put the acid in the jar?
Add the measured acid to the empty jar first, then pack in the tomatoes and liquid, leaving the headspace your recipe specifies.
Does salt affect canning safety?
No. Salt in canned tomatoes is for flavor only and can be left out. The acid is what makes the jars safe.
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This calculator gives standard tested acidification amounts for home-canned tomatoes. It does not replace a complete tested recipe or the correct processing method and time. Always follow the National Center for Home Food Preservation or your canner’s guide, and add acid to every jar of plain tomatoes, juice, or sauce. Spotted an error? Tell us here.