About the Home Canning Time & Altitude Adjuster
Every canning recipe prints its time for sea level. Live at 5,000 feet and that number is wrong, because water boils at about 203°F up there instead of 212°F, and a canner that never gets as hot has to run longer, or at higher pressure, to kill the same microbes. The USDA worked out the correction for each recipe separately. This tool looks it up for you.
Choose one of 42 USDA-tested processes (tomatoes, fruit, vegetables, meat and stock, pickles, jams), your canner (water bath, dial-gauge or weighted-gauge pressure), the pack and the jar. Set your elevation with a town or ZIP search, your device’s location or by typing it, and you get the exact minutes or psi from the USDA table for your altitude band, with the headspace and the page it came from.
What it will not do is equally deliberate. There is no custom-recipe mode, because a processing time is only valid for the recipe it was tested on. Low-acid foods are never given a water-bath time, since botulinum spores survive boiling. Oven, dishwasher and open-kettle canning are not offered at all. Every number was typed from the 2015 USDA guide and then checked by script against the PDF, cell by cell.
Every recipe in the tool, adjusted to your elevation for the canner you selected above. Print it for the inside of a cupboard door, or download it as a spreadsheet.
How to Use the Canning Altitude Adjuster
Pick the recipe first, because every USDA process belongs to one recipe and only that recipe. The canner buttons then show only the methods the USDA actually tested for it — water bath is greyed out for green beans, corn, meat and anything else low-acid. Choose hot or raw pack and the jar size; half-pints use the pint time, as the USDA guide specifies. Then set your elevation. The town or ZIP search asks the US Geological Survey’s elevation service for the ground height at that point, and Use my location does the same for where you are standing. If you know your elevation, just type it: a typed number always wins.
Why Altitude Changes the Process
Canning works by holding the whole jar at a known temperature for a known time. At sea level water boils at 212°F; at 2,000 feet it boils near 208°F, at 6,000 feet near 201°F and at 10,000 feet near 194°F. A water-bath canner can never be hotter than boiling water, so the only way to deliver the same lethality at a lower temperature is more time. That is why the tables add minutes above 1,000 feet — usually 5 minutes per band, though some recipes step differently, which is why this tool reads each recipe’s own row instead of applying a rule of thumb.
A pressure canner is corrected the other way. Its gauge reads pressure above the surrounding air. At altitude there is less air pushing down, so the same gauge reading gives a lower absolute pressure and a lower temperature inside. The USDA fix is to raise the gauge pressure: a dial gauge goes up 1 psi for every 2,000 feet (11 psi near sea level to 14 psi at 6,001–8,000 feet for low-acid food), while a weighted gauge, which only regulates at 5, 10 or 15 psi, jumps to the next weight above 1,000 feet. The processing time for a pressure canner does not change with altitude.
Botulism Is the Reason for All of This
Clostridium botulinum spores are on most fresh produce and survive boiling. In a sealed, moist, low-oxygen jar kept at room temperature they can germinate and produce botulinum toxin, one of the most potent poisons known, often with no smell or visible sign. Acid stops them: foods at or below pH 4.6 (most fruit, properly acidified tomatoes, pickles, jams) can be made safe at boiling temperatures. Everything above pH 4.6 — vegetables, meat, poultry, stock, and mixtures such as spaghetti sauce — has to reach 240–250°F, which only a pressure canner can do. The USDA puts the time needed to make low-acid food safe in boiling water at 7 to 11 hours, which is why no such process exists.
Methods This Tool Will Never Give You a Time For
- Oven canning — dry oven heat transfers poorly into jars and ovens cycle; jars can also shatter.
- Dishwasher “processing” — a dishwasher never gets near boiling for long enough.
- Open-kettle canning and jar inversion — filling hot jars and letting the lid seal kills nothing that is already in the jar.
- Your own recipe — changing ingredients, proportions or thickness changes how heat moves through the jar. Mashed pumpkin, thickened chili and extra onions in salsa are the classic examples. The published time is only valid for the published recipe.
Getting the Elevation Right
Use the elevation of the kitchen where you actually process, not your city’s official figure — towns in the mountains can span 1,000 feet or more. The lookup reads the USGS 3D Elevation Program model for the exact point you pick; when the USGS has no value (outside the US, or during an outage) it falls back to the Open-Meteo global elevation model and says so. If you are within 100 feet of a band boundary the tool tells you, and choosing the higher band is the cautious move: extra processing costs a little texture, never safety.
Fermenting instead of canning? The Fermentation & Pickle Brine Calculator handles salt percentages. For how long jars, leftovers and freezer food keep, see the Food Storage Guide, and for what is in season to can this month, the Produce Seasonality Finder. Browse every Cooking & Kitchen tool for more.
Processing times and pressures are reproduced from the USDA Complete Guide to Home Canning (2015 revision) as published by the National Center for Home Food Preservation. Follow the full recipe procedure in the guide, including acidification, headspace and venting. When in doubt, your county Cooperative Extension office can test a dial gauge and answer questions about your altitude.
Frequently Asked Questions
Why does altitude change canning times?
Water boils at a lower temperature the higher you live: about 212°F at sea level, 208°F at 2,000 feet and 201°F at 6,000 feet. A water-bath canner can never get hotter than boiling, so above 1,000 feet the USDA tables add processing minutes to deliver the same kill. A pressure canner works the other way: the gauge reads pressure above the surrounding air, and thinner air means the same gauge reading produces a lower temperature, so the USDA tables raise the pressure instead — a dial gauge by 1 psi per 2,000 feet, a weighted gauge from 10 to 15 psi above 1,000 feet.
Can I water-bath can green beans, corn or meat if I process them longer?
No. These are low-acid foods (pH above 4.6), and the spores of Clostridium botulinum survive boiling-water temperatures. The USDA guide puts the time needed to make low-acid food safe in a boiling-water canner at 7 to 11 hours, which is why no such process is published. Low-acid foods must be pressure canned at 240–250°F. This tool will not offer a water-bath time for them.
Why do tomatoes need lemon juice even in a pressure canner?
Some tomato varieties now test slightly above pH 4.6, the line below which botulinum cannot grow. The USDA tomato processes, including the pressure options, were calculated for acidified tomatoes: 1 tablespoon of bottled lemon juice or 1/4 teaspoon of citric acid per pint, twice that per quart, added to the jar. Skipping the acid invalidates every tomato time in the guide.
What is the difference between a dial gauge and a weighted gauge?
A dial gauge shows the pressure as a needle and can be set to any pressure, so the USDA tables step it up 1 psi for every 2,000 feet. A weighted gauge only regulates at 5, 10 or 15 psi, so it cannot be fine-tuned: above 1,000 feet you move up to the next weight, which is why weighted-gauge canners run at 15 psi for most low-acid foods at altitude. Dial gauges should be tested for accuracy every year; a gauge reading more than 2 psi off should be replaced.
Can I can in the oven, the dishwasher, or by turning jars upside down?
No. The USDA guide lists oven canning, dishwasher processing and open-kettle canning (filling hot jars and relying on the lid to seal) as methods that do not prevent spoilage. None of them reliably heats the center of the jar to a known temperature for a known time. They are not offered here, and no altitude adjustment can make them safe.
