If you live at sea level, altitude adjustments for canning are something you probably never think about. But if you live above 1,000 feet (and that includes a lot of the world!) skipping this step could mean your jars aren’t as safe as you think, even when everything looks perfectly fine.
The good news is that once you understand why altitude matters and know the right adjustments for your location, it becomes second nature. And I’ve built a free interactive tool that does all the math for you.
Why Does Altitude Affect Canning?
Here’s the science, kept simple: water boils at 212°F at sea level. That’s the temperature that every tested canning recipe is written for, because that’s the heat needed to safely process your food.
As altitude increases, air pressure decreases – and lower air pressure means water boils at a lower temperature. At 2,000 feet, water boils at around 208°F. At 5,000 feet, it’s about 203°F. That might not sound like much, but to heat-resistant bacteria, those missing degrees are the difference between being destroyed and surviving inside your sealed jar.
The jar still seals. The food still looks completely fine. But without the right adjustments, it may not be safe.
The USDA and the National Center for Home Food Preservation (NCHFP) set the adjustment threshold at 1,000 feet. Below that, the boiling point is close enough to 212°F that standard recipe times work. Above 1,000 feet, adjustments are required.
Altitude Adjustments for Water Bath Canning
Water bath canning is for high acid foods such as fruit and pickled vegetables.
For water bath canning, altitude adjustments mean adding extra processing time. The longer processing time compensates for the lower boiling temperature – you’re giving the heat more time to do its job.
Here’s where it gets a little more nuanced than most online calculators show: the adjustment depends on how long your recipe processes at sea level.
Recipes that process for less than 20 minutes
• 1,001-6,000 feet: add 5 minutes
• Above 6,000 feet: add 10 minutes
Recipes that process for 20 minutes or longer
• 1,001-3,000 feet: add 5 minutes
• 3,001-6,000 feet: add 10 minutes
• Above 6,000 feet: add 15 minutes
Jams, jellies, and preserves
Jellied fruit products have their own special rule: add 1 minute of processing time for every 1,000 feet above 1,000 feet. So if you’re at 4,000 feet making berry jam, you’d add 3 extra minutes to whatever your recipe calls for.
Altitude Adjustments for Pressure Canning
Pressure canning is for high acid foods such as beans, vegetables, and meats.
Altitude adjustments for pressure canning works differently than it does for water bath canning. Here, you don’t change the processing time – you increase the pressure. The higher pressure compensates for lower air pressure at altitude by pushing the temperature inside the canner high enough to destroy harmful spores, including those that cause botulism.
The adjustment depends on what type of pressure canner you have:
Dial gauge canners
• 0-2,000 feet: 11 lbs
• 2,001-4,000 feet: 12 lbs
• 4,001-6,000 feet: 13 lbs
• 6,001-8,000 feet: 14 lbs
• Above 8,000 feet: 15 lbs
Weighted gauge canners
• 0-1,000 feet: 10 lbs
• Above 1,000 feet: 15 lbs
Weighted gauge canners only come in 5, 10 and 15lb increments, which is why the jump goes straight to 15 lbs above 1,000 feet. With a dial gauge, you have more precision and can step up in smaller increments.
Use This Free Tool to Find Your Exact Adjustments
Rather than looking up tables and doing the math yourself every time you can, I built a free interactive tool that handles it all. Just enter your zip code or altitude, plug in your recipe’s processing time and PSI, and it gives you your exact adjusted numbers – including a special calculation for jams, jellies, and preserves.
The tool covers both water bath canning and pressure canning, handles both dial gauge and weighted gauge canners, and correctly applies the different adjustment tables for short-process vs. long-process recipes.
If you’re using a steam canner, enter the processing time in the water bath canning section. Please note that the adjusted time cannot be more than 45 minutes when using a steam canner.
Altitude Adjustment Tool
Enter your altitude and recipe details to get your exact adjusted canning times and pressures.
Frequently Asked Questions
If you live in the US, the easiest way is to use the tool above – just enter your zip code and it looks it up automatically. Outside the US, you can Google your city name + “altitude” or check with your local county extension or ag office.
Yes. The NCHFP guidelines are clear: if you’re above 1,000 feet, adjustments are needed. It’s not worth the risk to skip them, even if you’re only a few hundred feet above the threshold.
No. Standard recipe pressures (10 lbs for weighted gauge, 11 lbs for dial gauge) apply at sea level to 1,000 feet. No adjustment needed. Use whatever pressure the recipe recommends without adjustments.
Most simplify the water bath adjustment into a single number regardless of recipe time, which isn’t accurate. The correct tables – from NCHFP and university extension services – show that the adjustment depends on whether your recipe processes for under or over 20 minutes. Or they don’t account for differences in dial gauge and weighted gauge canners. This tool accounts for all those nuances.
One More Think to Tuck Into Your Safe Canning Routine
Altitude adjustments are one of those things that feel complicated the first time you look them up, but once you know your numbers they become automatic. Bookmark the tool above so it’s always handy, and use it every time you try a new recipe.
Safe canning isn’t about being intimidated by the rules – it’s about understanding why they exist so you can follow them with confidence. And now you know the why.
Happy canning!
Sources:
University of Kentucky Cooperative Extension, FCS3-591 – Safe Home Canning: Altitude Adjustments.
National Center for Home Food Preservation
SDSU Extension – Altitude Adjustments for Home Canning.
Angi Schneider is the author of The Ultimate Guide to Preserving Vegetables and Pressure Canning for Beginners and Beyond, both published by Page Street Publishing. She has taught canning classes for 177 Milk Street, been featured in Serious Eats, and written for Countryside Magazine. Angi has been sharing gardening, preserving, and simple living skills since 2010.