Minimum load guidance is good practice.  

Several years ago, Ball published new guidance for the minimum number of jars (“minimum load”) that should be processed in each pressure canner load, stating that in order to ensure that proper pressure and temperature is achieved for safe processing, the pressure canner should be filled with at least 2 quart or 4 pint jars. Recently, Presto updated their guidance, saying “Presto stovetop canners have a minimum jar capacity of 2 quarts or the equivalent if using smaller jars. This is to maintain enough mass in the canner for an adequate cool down period.”

As of this writing, the guidance from Ball and Presto has not been endorsed by the NCHFP, USDA, or university Cooperative Extensions. However, adhering to a minimum load of 2 quart jars or the equivalent is certainly not a bad practice: the cool down period is part of the overall thermal processing, and an adequate natural cool down time contributes to a safe canned product. Furthermore, the more jars there are in a pressure canner, the more space is filled and the quicker it will vent (and the less time the food in the jars will be subjected to heat). Our experience has also shown that a very small canner load can be difficult to bring up to required pressure and risks the water in the canner running dry. If you are pressure canning a small batch of food, you can add jars of water to meet the canner minimum jar load (and if you don’t plan on saving the canned water, there is no need to apply a lid). 

Note that the minimum load guidance is different from the the minimum physical size requirements of pressure canner. To be considered a pressure canner, the device should hold at least 4 quart jars standing upright on a rack with the lid secured. 

For further information on preserving visit the National Center for Home Food Preservation (NCHFP) or contact your local Cooperative Extension office. 

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Updated July 2025