This time of year we get many calls to calibrate an ovens temperature. In most cases, this is something you can do yourself. We recommend using two of the small round oven thermometers https://amzn.to/33QPXTB. Most ovens have a calibration mode where you can adjust the temp up or down by as much as 35 degrees. Put the oven thermometers in the oven on the middle shelf and turn the oven on to a temp that you like to cook at, usually 350 to 400. Give the oven 30 minutes to an hour for the most accurate results. Check and see what the temps are on the oven thermometers. Hopefully they are the same… If the temp is off by 30 degrees or less, it can be calibrated. If its off more than that, you need service. Your user manual should have instructions on calibration. If you don’t have the user manual, most are available on line at the manufacturers website.