How to Use the Canning Altitude Adjustment Calculator
Enter your altitude in feet above sea level, select your canning method (water bath, pressure dial gauge, or pressure weighted gauge), and enter the base processing time from your recipe. For pressure canning, also enter the base pressure specified in the recipe (usually 10 PSI). The calculator applies USDA-recommended adjustments to give you the correct processing time or pressure for your altitude.
This tool is essential for anyone canning above 1,000 feet elevation. Using sea-level processing times at higher altitudes can result in improperly processed food, creating a food safety risk. Always follow tested recipes from reliable sources such as the USDA Complete Guide to Home Canning, the National Center for Home Food Preservation, or your local Cooperative Extension Service.
Why Altitude Matters for Canning
At higher altitudes, atmospheric pressure decreases, which lowers the boiling point of water. At sea level, water boils at 212 degrees F (100 degrees C). At 5,000 feet, it boils at about 203 degrees F. This lower temperature means the heat treatment during water bath canning is less intense, so additional processing time is needed to ensure harmful organisms are destroyed. For pressure canning, increased pressure compensates by raising the boiling point back to safe levels.
Water Bath vs. Pressure Canning
Water bath canning is suitable only for high-acid foods with a pH of 4.6 or lower, such as fruits, pickles, salsas, jams, and jellies. The boiling water (212 degrees F at sea level) is hot enough to destroy molds, yeasts, and some bacteria in acidic environments. Low-acid foods (vegetables, meats, poultry) require pressure canning, which reaches 240 degrees F at 10 PSI, killing Clostridium botulinum spores.
Frequently Asked Questions
Why does altitude affect canning?
Water boils at a lower temperature at higher altitudes, so bacteria and spores are not killed as effectively. Processing times or pressures must increase.
How much extra time for water bath canning at altitude?
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.
How does altitude affect pressure canning?
Dial gauge: increase by 1 PSI per 2,000 ft above 1,000 ft. Weighted gauge: use 15 PSI instead of 10 above 1,000 ft.
Can I use a water bath canner for low-acid foods?
No. Low-acid foods must use a pressure canner to reach 240 degrees F to destroy botulism spores.
How do I find my altitude?
Search your city or zip code with "elevation" in any search engine, use a GPS app, or check with your county extension office.