Canning altitude calculator

Why adjust canning for altitude?

Water boils at a lower temperature at higher elevations. The National Center for Home Food Preservation warns that food may spoil if you do not add process time for boiling-water canning above 1,000 feet; in a pressure canner you raise the pressure instead.

What pressure do I use with a dial gauge?

For recipes processed at 11 pounds at sea level, such as green beans: 11 lb up to 2,000 ft, 12 lb at 2,001–4,000 ft, 13 lb at 4,001–6,000 ft and 14 lb at 6,001–8,000 ft (NCHFP).

And with a weighted gauge?

For the same recipes: 10 lb up to 1,000 ft and 15 lb above 1,000 ft. Weighted gauges come in fixed steps, so there is nothing in between.

How much time do I add in a boiling-water canner?

It depends on the food and the jar, so use the table in the tested recipe. For hot-packed peaches in quarts, NCHFP gives 25 minutes up to 1,000 ft, 30 at 1,001–3,000 ft, 35 at 3,001–6,000 ft and 40 above 6,000 ft.

How long do I sterilize empty jars?

NCHFP: boil 10 minutes at elevations under 1,000 feet, and 1 more minute for each additional 1,000 feet.

How much lower is the boiling point at my elevation?

A rule of thumb from Colorado State University Extension is that water boils about 2°F lower for every 1,000 feet above sea level. At 5,200 ft that is about 201.6°F instead of 212°F. A lower boiling temperature means a boiling-water canner is less hot, which is why it needs more time.

How often should a dial gauge be tested?

Extension services recommend testing a dial gauge every year before the canning season, and replacing it if it reads more than 2 pounds off. A weighted gauge does not need testing, because the weight sets the pressure.

Can I use the sea level time at altitude with a pressure canner?

Yes. In a pressure canner the processing time stays the same, and the adjustment is made to the pressure. In a boiling-water canner it is the other way: the pressure is fixed by the atmosphere, so the time goes up.

How it works

Air pressure falls as elevation rises, and water boils at a lower temperature. A pressure canner makes up the difference with higher gauge pressure, so the food inside reaches the same temperature as at sea level. The calculator uses the National Center for Home Food Preservation (NCHFP) tables, which depend on the type of gauge. A dial gauge reads the pressure directly and is adjusted in steps by elevation band. A weighted gauge works in fixed pressure steps, so it has only two settings. The sterilizing time for empty jars is 10 minutes below 1,000 ft plus one minute per 1,000 ft. The tables are for recipes that call for 11 lb (dial) or 10 lb (weighted) at sea level; the calculator also covers recipes that call for 6 lb or 5 lb.

Worked example

You live at 5,200 ft (1,585 m). For a recipe that calls for 11 lb on a dial gauge at sea level, the setting at this elevation is 13 lb. On a weighted gauge it is 15 lb. For a recipe that calls for 6 lb at sea level on a dial gauge, the setting is 8 lb. Empty jars to be sterilized should boil 15 minutes (5,200 ft is between 5,000 and 6,000 ft, so 10 + 5). Water boils at about 201.6°F here instead of 212°F.

Common mistakes

• Using the sea level recipe unchanged. Food canned at too low a temperature or for too short a time may not be safe to store. Always adjust.
• Mixing up elevation and the recipe's pressure. The pressure table depends on the pressure the recipe calls for at sea level. Choose the table that matches your recipe.
• Using a dial gauge that has not been tested. An inaccurate gauge reads the wrong pressure, so the adjusted setting does not give the right temperature.

Sources and related calculators

Pressure and sterilizing tables: National Center for Home Food Preservation (University of Georgia) and the USDA Complete Guide to Home Canning. Boiling point rule: Colorado State University Extension. This tool does not replace a tested recipe. Related: brine calculator, candy temperature calculator and chicken cooking time calculator.