Canning Altitude Adjustment Calculator
Adjust a tested recipe's water-bath time or pressure canner psi for your altitude, using exact USDA/NCHFP tables.
This adjusts a tested recipe's time for your elevation; it does not replace one. Only use this for high-acid foods that are safe to water-bath can in the first place.
How it works
Water boils at a lower temperature the higher up you are, and a pressure canner reaches a lower maximum temperature at a given pressure too. Both USDA and the National Center for Home Food Preservation (NCHFP) publish altitude tables that correct for this, and this calculator just looks up the number for you instead of you squinting at a chart on the stove.
For water-bath canning, enter your altitude and the tested recipe's processing time. Say your recipe calls for 25 minutes and you can at 4,500 ft. That altitude falls in the 3,001 to 6,000 ft band, which adds 10 minutes, so the calculator tells you to process for 35 minutes total. For pressure canning, pick your gauge type instead. A weighted gauge stays at 10 psi up to 1,000 ft and jumps to 15 psi above that; a dial gauge climbs in finer steps, from 11 psi near sea level up to 14 psi above 6,000 ft. Either way, the time in the recipe stays the same. Only the pressure changes.
Not sure of your altitude? A quick web search for "elevation" plus your town name, or a phone weather app, will get you close enough. These tables are banded in thousand-foot chunks, so being off by a hundred feet or so won't change your result.
FAQ
Do I really need to adjust for altitude?
Yes, if you live above 1,000 ft. Below that, no adjustment is needed for either method. Above it, skipping the adjustment means your jars may not reach a temperature high enough to destroy spoilage organisms and, for low-acid foods, the bacteria that cause botulism.
Why does pressure change but not time, for pressure canning?
A pressure canner is sealed, so the pressure inside determines the temperature the jars actually reach, not how long you cook them. At higher altitude, a given pressure produces a slightly lower temperature, so the fix is to raise the pressure, not extend the clock. Water-bath canning works the opposite way: it's always at the boiling point of water for your elevation, so the only lever you have is more time.
Can I use this calculator instead of a tested recipe?
No. This tool only adjusts a tested recipe's numbers for your elevation; it doesn't supply the recipe itself. Always start from a current, tested source like the USDA Complete Guide to Home Canning, NCHFP, or Ball, and never can a low-acid food (plain vegetables, meats, poultry, seafood, or soups) using a water bath, no matter what the altitude adjustment says.
What if my altitude falls right on a boundary?
The tables are inclusive of their upper number, so 3,000 ft uses the 1,001 to 3,000 ft band and 3,001 ft moves into the next one. When in doubt, round up to the higher band. A few extra minutes of processing or one extra pound of pressure never hurts; falling short can.
For more background, see how to adjust canning for your altitude, dial-gauge vs. weighted-gauge pressure canners, and why you can't water-bath can low-acid foods.