As altitude increases, the temperature that can achieved at a given pressure will decrease.
Consequently, as altitude increases, you have to also increase the pressure inside the pressure canner to reach and maintain a desired temperature. You leave the processing time as is.
Sea level is the base
Sea level for canning purposes is deemed to be 0 to 1000 feet (0 to 300 metres). Giving processing pressure for sea level processing is the default in pressure canning recipes. (Note that some publications in some high altitude areas such as Colorado or Utah may give recipes with the pressure already adjusted specially for that area.)
A USDA bulletin from the 1970s, though dated, is still valid in its explanation of how this all works:
Atmospheric pressure is like the thickness of frosting on a cake. Where it is thickest it weighs more per square inch than where it is thin. At sea level, where the atmosphere is the thickest, it is heavier than atop a mountain.
As altitude increases, atmospheric pressure or its weight per square inch decreases. Altitude affects the boiling point of water. Where altitude is least, at sea level, water boils at 212° F [100 C]. As altitude increases the boiling point of water decreases.
The same is true in a pressure canner. Under 10 pounds pressure at sea level, water boils at 240° F [115 C]. As altitude increases, the temperature in a pressure canner at 10 pounds of pressure is less than 240°F [115 C]. This difference is enough to affect the safety of canned products at altitudes above 2,000 feet.” [1] Tope, Nadine Fortna. Pressure Canners, Vital for Low-Acid Foods. In: Growing, Freezing, Storing Garden Product. USDA Information Bulletin 410. 1977. Page 324 – 325.
Finding your altitude for canning
You can use Google maps to find your altitude. You can enter your entire address in: e.g 123 Queen Street, Upper Lower Bottom, Wisconsin, USA.
Dial gauge versus weighted gauge
With dial gauges, you can increase the pressure used in small increments.
With weighted gauges, because the weights are only made in 5 lb increments, you must increase the pressure in blocks of 5 lbs (35 kPa).
The following charts represent the pressure required at your altitude to reach 240 F / 115 C inside your canner. Processing time is the same at all altitudes once the correct pressure for those altitudes is applied.
Pressure Canning Meat, Vegetables, Fish, Seafood, Soup: Altitude and Pressure Chart
| Altitude feet / metres | Weighted Gauge lb | Dial Gauge lb | Weighted Gauge kPa | Dial Gauge kPa |
|---|---|---|---|---|
| 0 - 1000 / 0 - 305 | 10 | 11 | 69 | 76 |
| 1001 - 2000 / 306 - 609 | 15 | 11 | 103 | 76 |
| 2001 - 4000 / 610 - 1219 | 15 | 12 | 103 | 83 |
| 4001 - 6000 / 1220 - 1828 | 15 | 13 | 103 | 90 |
| 6001 - 8000 / 1829 - 2438 | 15 | 14 | 103 | 97 |
| 8001 - 10000 / 2439 - 3048 | 15 | 15 | 103 | 103 |
Pressure Canning Fruit: Altitude and Pressure Chart
| Altitude feet / metres | Weighted Gauge lb | Dial Gauge lb | Weighted Gauge kPa | Dial Gauge kPa |
|---|---|---|---|---|
| 0 - 1000 / 0 - 305 | 5 | 5 | 35 | 35 |
| 1001 - 2000 / 306 - 609 | 10 | 6 | 69 | 42 |
| 2001 - 4000 / 610 - 1219 | 10 | 7 | 69 | 49 |
| 4001 - 6000 / 1220 - 1828 | 10 | 8 | 69 | 56 |
| 6001 - 8000 / 1829 - 2438 | 10 | 9 | 69 | 62 |
| 8001 - 10000 / 2439 - 3048 | 10 | 69 |
Caution: to be clear, this second table is for fruits. See first table for all else. It is the USDA Complete Guide and So Easy to Preserve that give pressure canning alternatives for fruit. Use this altitude table only with the fruits they explicitly list for pressure canning.
See also: Altitude Adjustments for Water Bath and Steam Canning
Sources
Ball Blue Book. Muncie, Indiana: Healthmark LLC / Jarden Home Brands. Edition 37. 2014. Page 9.
Bernardin Guide to Home Preserving. Toronto, Canada: Bernardin Ltd. 2013. Page 12.
Bernardin. Canning at high altitudes. (Metric conversions. Accessed February 2015.)
National Presto Industries. Presto Pressure Canner and Cooker Manual. 2014. (Fruit pressure chart, page 25)
United States Department of Agriculture (USDA). Complete guide to home canning. Agriculture information bulletin No. 539. 2015. Pages 1-8 and 22 – 23.
References
| 1. | ↑ | Tope, Nadine Fortna. Pressure Canners, Vital for Low-Acid Foods. In: Growing, Freezing, Storing Garden Product. USDA Information Bulletin 410. 1977. Page 324 – 325. |
I live in Knoxville Tn and I need to know how many pounds of pressure I need here for canning please for all of my pressure canning. Thank you so much.
I have just found out that I’ve been canning my dried beans at 10# when they should have been 15#….
So I have about 45 its here done…..
What should I do next? Can I just reprocess them?
My stove has a really hard time getting to 15#… IT takes about 90 minutes just to get up to pressure.
Those jars would be underprocessed. Please check with one of these Master Food Preserver help groups.
I have a small pressure cooker. Can and how do I can sweet potatoes in pint jars????
A pressure cooker is not a pressure canner. https://www.healthycanning.com/pressure-cookers-versus-pressure-canners/
Here are directions for freezing them: https://nchfp.uga.edu/how/freeze/potato_sweet.html
I don’t have a pruesser canner so what is the best one for me? I live between 3000 ft. an 6000 ft.?
These particular adjustments apply only when using genuine pressure canners.
I have never used a pressure canner in my life .. little bit afraid , I mean a lot afraid.. but here is my question I live in southern Ontario Canada.. how do I find out my altitude an amount of pressure needed to safely can with my new PC
Type into google search “What is the altitude for Turkey Point” (or whatever the town is where you live.) If you need advice about what models of pressure canners are available at stores at what stores in the area, let us know.
You can go online and google what is the altitude of your city
I live in Greece my sea level is 1300 feet,I have a presto 16 my weight doesn’t wiggle I do not now what to do.
Thank you Marion
The default weight that ships with the Prestos is 15 lbs, which is the pressure you need (as you know) at 1300 feet. I’m surprised it is not wiggling. Do you have to wait longer for the pressure to build up enough?
I don’t get it. Here are my numbers from google. 11,45.14517821629582,-88.58470720054356,320.347,1051.008,89
so what do I do with this number, I don’t see it listed in the table. We are usually canning at 10# of pressure
What altitude at you at? https://www.whatismyelevation.com/