Free water bath canning calculator. Enter jars to find the canning water you need and how many canner batches your jars will take.
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Enter the number of jars you want to can. This water bath canning calculator plans 1.5 litres of canning water per jar and 7 jars per canner batch, so it gives total water and the number of batches at once. Use the water level and altitude sections below before you start: jars must stay covered by 1 to 2 inches of water for the whole process, processing time rises with altitude, and only high acid foods belong in a water bath canner. This calculator is a planning estimate only: always follow a tested recipe for your food and jar size.
How much water for canning is usually answered as a rule, not a fixed per jar figure: start with the canner about half full, add the jars, then top up so jars are covered. This canning water calculator turns that rule into a planning estimate of 1.5 litres per jar, so 7 jars need 10.5 litres and 8 jars need 12.0 litres. Always measure your own pot in practice, because jar size and pot shape change the real volume, and the 1 to 2 inch cover rule in the next section is the safety check that matters most.
How many jars can I can at once? A standard 21 quart canner holds 7 quart jars or 8 to 9 pint jars in a single layer, and larger canners hold up to 14 quart jars. This calculator uses 7 jars per batch, so 7 jars need 1 batch and 8 jars need 2 batches. How many batches to can 20 quart jars? At 7 jars per batch, 20 jars need 3 batches (7 plus 7 plus 6). Never stack quart jars unless your canner instructions and a tested recipe allow it, and always use a rack so jars do not sit directly on the pot bottom. Canner capacity is set by inside diameter and depth, not by the printed quart size alone, so measure your pot before trusting a capacity label.
Water bath canner water level is the key safety rule: jars must be covered by 1 to 2 inches of water for the whole processing time. Use 1 inch of cover for short processes of about 10 to 20 minutes and 2 inches for longer processes, because water evaporates during a long boil. How deep should water be over canning jars? At least 1 inch, and 2 inches is safer for long processes. If the level drops, top up only with boiling water from a kettle, never cold water, which can crack jars and stop the boil.
Do jars need to be covered with water when canning? Yes, for water bath canning, jars must stay fully submerged, because the boiling water is what heats the food evenly and drives air from the jars. For pressure canning the rule is different: jars are not submerged, and only 2 to 3 inches of water is used, because steam does the work. What happens if water does not cover jars in canning? The exposed part may not reach a safe temperature, seals may fail, and the batch may not be safe to store, so keep the water level checked through the whole process.
Canning altitude adjustment matters because water boils at a lower temperature as altitude rises, about 1 degree Fahrenheit lower per 500 feet. For water bath canning, add 5 minutes for 1,001 to 3,000 feet, 10 minutes for 3,001 to 6,000 feet, 15 minutes for 6,001 to 8,000 feet, and 20 minutes for 8,001 to 10,000 feet, with no added time below 1,000 feet. Find your altitude from your city elevation or a map tool before you start, and use the adjusted time for the full process, not just part of it.
Water bath canning is only safe for high acid foods with a pH of 4.6 or below, such as jams, jellies, pickles, fruit preserves and tested tomato recipes. Low acid foods such as vegetables, meat, beans and soups must be pressure canned, because a water bath cannot reach a safe temperature for them no matter how long it boils. Never water bath a low acid recipe, and never guess a processing time: use a tested recipe from a trusted canning source for your exact food, jar size and altitude.
For 7 jars, this calculator gives 10.5 litres of water and 1 batch, which matches a standard 21 quart canner holding 7 quart jars. For 8 jars, it gives 12.0 litres and 2 batches, because the eighth jar starts a second batch. In practice, start with the canner about half full, load the jars on the rack, top up with hot water to 1 to 2 inches above the lids, leave about 2 inches of headroom to prevent boil over, and keep a kettle of boiling water ready for top ups.
Common mistakes are starting with too little water, letting the level fall below the lids, adding cold water during processing, skipping the rack, and canning low acid foods in a water bath. Other mistakes are reusing flat lids, which should be new each time, and using jars that are not made for canning. Check seals after cooling, store sealed jars without bands in a cool dark place, and refrigerate or discard any jar that did not seal.
Start with the canner about half full, add the jars, then top up with hot water so jars are covered by 1 to 2 inches. This calculator plans about 1.5 litres per jar as an estimate, but always check the water level in your own pot before you start the boil.
Yes, for water bath canning jars must stay fully submerged for the whole process. If water drops below the lids, top up only with boiling water, and never let jars sit partly exposed during processing.
A standard 21 quart canner fits 7 quart jars or 8 to 9 pint jars in a single layer, and larger canners fit up to 14 quart jars. Wide mouth quart jars fit fewer per batch than regular mouth quart jars, because they are wider.
A 21 quart water bath canner usually holds 7 quart jars, 9 pint jars, or 12 half pint jars. Check your canner model, because inside diameter and depth change the fit, and depth often limits quart jars first.
It depends on your canner: 7 quart jars per batch is the standard planning figure used here. Divide your total jars by jars per batch and round up: 20 jars at 7 per batch need 3 batches.
The exposed part of a jar may not reach a safe temperature, seals may fail, and the food may not be safe to store. Keep jars covered by 1 to 2 inches for the whole process and top up with boiling water if the level falls.
Water boils cooler at altitude, so add processing time: 5 minutes for 1,001 to 3,000 feet, 10 minutes for 3,001 to 6,000 feet, 15 minutes for 6,001 to 8,000 feet, and 20 minutes for 8,001 to 10,000 feet. Below 1,000 feet, add no time.
No. Vegetables, meat, beans and soups are low acid foods and must be pressure canned, not water bathed, because a water bath cannot reach a safe temperature for them. Use a water bath only for high acid foods with pH 4.6 or below, following a tested recipe.
No, use new flat lids for every batch, because the sealing compound works only once. Screw bands can be reused if they are not rusted or bent, but always check them before use.