Canning Processing Time Calculator
Adjust a tested boiling-water-bath canning time for your altitude, following USDA / National Center for Home Food Preservation altitude tables. For pressure canning, it keeps the tested time and tells you the pressure to use instead.
Last updated: September 2026
Formula below · 2 sources (fdc.nal.usda.gov, Wikipedia) · Updated Sep 2026
Compare with similar
About this calculator
Safe home canning starts from a tested recipe (USDA Complete Guide to Home Canning, the National Center for Home Food Preservation, or Ball) that gives a processing time for a specific food, preparation and jar size. Never scale a tested time by jar size or shorten it — the time was established by heat-penetration testing for that exact jar. For a boiling-water bath, water boils at lower temperatures at altitude, so the general USDA/NCHFP adjustment is to add 5 minutes at 1,001–3,000 ft, 10 minutes at 3,001–6,000 ft, 15 minutes at 6,001–8,000 ft and 20 minutes at 8,001–10,000 ft (if your recipe has its own altitude chart, use that). Formula: adjusted time = tested time + altitude minutes. For pressure canning, the processing time does not change with altitude; instead you raise the pressure: a weighted-gauge canner uses 10 psi at 0–1,000 ft and 15 psi above 1,000 ft; a dial-gauge canner uses 11 psi up to 2,000 ft, 12 psi at 2,001–4,000 ft, 13 psi at 4,001–6,000 ft, 14 psi at 6,001–8,000 ft and 15 psi at 8,001–10,000 ft. So for pressure canning the calculator returns your tested time unchanged. Low-acid foods (vegetables, meat, poultry, fish, beans) must be pressure canned; a boiling-water bath cannot destroy Clostridium botulinum spores in them. The jar-size field is a reminder only: look up the time for the jar size you are using.
How to use
Suppose your tested recipe says to process pint jars of tomatoes for 40 minutes in a boiling-water bath, and you live at 3,000 ft. Choose 1,001–3,000 feet and Boiling-water bath: adjusted time = 40 + 5 = 45 minutes. If the recipe gives 45 minutes for quarts, enter 45 when you use quart jars rather than scaling the pint time. For pressure-canned green beans with a tested time of 20 minutes for pints at 3,000 ft, the calculator returns 20 minutes; process them at 15 psi in a weighted-gauge canner or 12 psi in a dial-gauge canner at that altitude.
Frequently asked questions
Why does altitude affect canning processing time for home preserving?
At higher altitudes, atmospheric pressure is lower, which means water boils at temperatures below 212°F. At 3,000 feet, water boils at approximately 207°F; at 6,000 feet, around 201°F. Since heat is what destroys dangerous microorganisms and spoilage bacteria, a lower boiling point means less effective pasteurization in the same amount of time. Processing time must be extended to compensate so that the center of each jar receives sufficient lethal heat treatment. USDA-approved recipes include specific altitude adjustment tables for exactly this reason.
What is the difference between water-bath canning and pressure canning for processing times?
Water-bath canning uses boiling water (212°F at sea level) and is only safe for high-acid foods with a pH of 4.6 or lower, such as fruits, pickles, jams, and tomatoes with added acid. Processing times in a water bath range from 5 to 85 minutes depending on the food and jar size. Pressure canning reaches 240°F using steam under pressure and is required for all low-acid foods — vegetables, meats, poultry, and fish — because these temperatures are necessary to destroy botulism spores that survive boiling water. Mixing up the two methods is a serious food safety risk.
How do I know what base processing time to use for my canning recipe?
Base processing times should always come from tested recipes published by the USDA, the National Center for Home Food Preservation (NCHFP), or the Ball Blue Book of Preserving — never from untested family recipes or general internet sources. These times are established through laboratory testing that verifies adequate heat penetration to the cold spot of the jar for each specific food and preparation method. Using an unverified recipe risks under-processing, which can allow botulism toxin to develop in sealed jars. The base time in this calculator is the starting point; altitude and jar-size adjustments are applied on top of that validated figure.