Pressure cooker time & pressure
Common sterilization cycles at 15 psi, with the pressure bump growers use at elevation.
Start timing once the cooker reaches full pressure. Let it cool on its own before opening; venting fast can boil over agar and crack jars.
How this calculator works
At sea level, 15 psi gauge pressure reaches about 250 °F (121 °C), the standard temperature for sterilizing culture media and grain. Denser and larger loads need longer holds for heat to reach the center: liquid agar sterilizes quickly, while packed grain bags take the longest.
At elevation the air pressure is lower, so the same gauge reading reaches a lower temperature. A common rule is to add 0.5 psi for every 1,000 ft above sea level.
Common questions
How long do I sterilize grain jars?
About 90 minutes at 15 psi for quart jars and about 75 minutes for pints. 3 lb grain bags usually need around 2.5 hours.
When do I start the timer?
Once the cooker reaches full pressure. Heating up and cooling down don't count toward the hold time.
Can I open the cooker right away?
No. Let it cool and depressurize on its own. Venting fast can boil agar over and crack jars.
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