What Is the Difference Between a Pressure Canner and a Pressure Cooker?

A pressure cooker is meant to shorten cooking time. Pressure builds inside, raising water’s boiling point so food cooks at a higher temperature and tasks that would take hours take minutes. You do not need to know the exact pressure for this purpose; as long as the lid is hissing, the cooker is doing its job. Canning is a different matter. The question is not whether the food is cooked, but whether the center of the jar has stayed at a specific temperature for a specific length of time—and that cannot be determined by guesswork.

That is why a pressure canner’s first distinguishing feature is its pressure gauge. There are two types: a weighted gauge rocks at regular intervals and makes a sound when the set pressure is reached, regulating the pressure itself; a dial gauge displays the reading with a needle, and the user adjusts the heat while watching it. A dial gauge must undergo a calibration check at the start of every season, because a needle that reads incorrectly will not make it apparent that the jars were underprocessed. Most pressure cookers do not have such a gauge.

The second difference is capacity, which is easy to overlook. A pressure canner must be deep enough to hold jars upright and have a rack underneath to keep the jars off the bottom. The minimum accepted size is one that can hold at least four 1-liter jars upright. This is not only about capacity: a small volume heats and cools very quickly, causing pressure inside to fluctuate and changing how long heat reaches the center of each jar. A larger volume steadies these fluctuations.

Because a home pressure cooker lacks these two features, it is not used for low-acid canning. A recipe does not say “make it in a pressure cooker” because the pressure reached varies by model, cannot be measured, and the time tables were not prepared for those conditions. In addition, some models have two pressure settings, and users may not know which one they are using. The value printed on the appliance lid is a design target, not the pressure actually reached in the kitchen that day. Processing with unmeasured pressure is considered unmeasured, regardless of the processing time.

In practice, the distinction is as follows. Jam, marmalade, fruit compote, and vinegar-pickled vegetables are high-acid or acidified foods; they do not require pressure, and a boiling-water bath is sufficient—a regular deep pot will do. Low-acid foods such as beans, peas, corn, chickpeas, spinach, and meat are processed only in a pressure canner. There is no recommended method for canning vegetables that have not been pickled in a boiling-water bath, and a pressure cooker does not fill that gap.