Some ovens just can't be set perfectly so I don't drive myself crazy trying to get the temperature 'just right' but I do opt for the temperature being about 5 or 10 degrees too high rather than too low because most recipes turn out better baking a bit faster rather than too slowly (especially bread). All you need to do is check what you're baking a little earlier than the suggested amount of time accordingly. I've had both gas and electric ovens but have never calibrated a gas oven myself so these instructions are for electric ovens. ;) Electric ovens are fairly standard, so you should be able to figure out how your temperature adjustment knob works by reading these simple instructions. Here's how to calibrate an electric oven:
Put the oven thermometer on the center rack of the oven, set the temperature to 350 degrees F and let it run for a half hour. Check the thermometer to see whether it reads 350 degrees or not. If it doesn't read 350 degrees, turn off the oven and let it cool off while leaving the thermometer on the oven rack. (If you find your oven happens to be 50 degrees or more off, whether too low or too high, you most likely will need an appliance repair person to replace the oven thermostat.)
Pull the oven temperature knob off from the stove top temperature control area. You may need to use a flat head screwdriver or butter knife to gently lift it off. The thermostat calibration dial will be located on the back of the knob. On the back of the knob there will be clips or screws locking it in place. Loosen these clips or screws and adjust the dial as needed to increase or decrease the temperature. For most electric ovens the dials have slash marks or it 'clicks', and each mark or click is for 10 degrees and you should be able to see the words 'low' on the left of the slashes and 'high' to the right of the slashes or a '+ or -'. Adjust accordingly and put the clips or screws back in place and the knob back on the stove top control shaft. Turn the oven back on and re-test the oven again for a half an hour to see the oven's temperature adjustment difference. If the oven thermometer still does not read 350 degrees F, adjust the calibration dial again and re-test the oven until it is at as accurate of a temperature as possible.
Happy Baking! ;-)
By Deeli from Richland, WA