Oven tempperature is off anywere from 50 to 100 degrees. varies with setting

The temperature for the TCO in your fan oven should be set to the desired cooking temperature for your recipe. This will depend on the type of food you are cooking and the recipe you are following.

For example, if you are baking bread, a typical temperature would be between 350-450 degrees Fahrenheit. If you are roasting a chicken, a common temperature is 375-400 degrees Fahrenheit. If you are cooking a casserole, a good starting point is 350 degrees Fahrenheit.

It's important to follow the recipe or guidelines for the specific type of food you are cooking, as the correct temperature and cooking time will vary based on the ingredients and method

temperature settings in ovens vary make to make
set around the receipe recommended temp but remember that most on tv cooks always say around the temp ( around 180 or around 250 for about 1hour or about 10 minutes
When cooking , nothing is set in concrete so to speak

very normal but only during pre heat / once the oven is stable tempt should be 5 to 10 deg above and below the tempt setting and if not replace the oven temp sensor located inside the oven on the back ..mm

this is most likely a bad thermostat

There is a calibration method to adjust the oven thermostat plus/minus 35 degrees if it is a digital display. The method varies depending on the model range. This calibration method is used to adjust the thermostat if it is not keeping proper tempature. For example if you are setting the oven to 350 and the actual temp it is keeping is 325 then you could use the calibration method to adjust it plus 25 degrees to correct the temp. Just so you know electric ovens will keep a pretty even temp but gas ovens will vary by 40 or more degrees to keep an "average" temp. For example the burner will come on when the oven is 330 degrees and turn off at 370. 330+370 then divide by 2=350. So a oven thermometer may not show you the temp you set it at in a gas oven but does not mean the oven temp is off.

You will need to check the oven calibration using a thermocouple based thermometer(the one you stick in the oven is not reliable). Electric ovens should keep a near constant tempature so if you have it set to 350 the oven should stay around 350 once temp is reached. Now gas ovens are a little different. Most use a on/off thermostat and that means the temp can vary from 320 degrees to 370 degrees to keep an average tempature of 350. So if it is a gas oven you will need to let it warm-up for 10 minutes then start taking the lowest and highest 5 consectutive readings. Then add the 5 reads together and then divide the number by 5 and it should be within 10 degrees of the set tempature. If it is off by more than 50 degrees then you might not be able to get it back to proper calibration. The calibration methods are different for each range and depend on the type of thermostat you have digital(push button controls) or manual(knob). The owner's manual for your range might contain the instructions or consult the manufacture's website for the instructions.

Replace the thermostat, and it should solve your problem.
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Thanks.

Perhaps the item you are using to check temperatures is not accurate. I my line of work, I use a digital thermometer which records immediate temperature. Perhaps understanding the process will help you see more accuracy in the way you read the temperature in your oven. Allow me to offer this explanation....First of all, place your thermometer near on the top rack as close to the oven temperature probe as possible. This probe is the focal point for your oven and detects the temperature and opens the electrical circuit to turn off the element when the desired set temperature is attained. Set your electric oven to 300 degrees and hopefully, you have a window in your oven to watch. The bake element will come on and the temperature will rise until it reaches 300 degrees. It is at this point when your oven bake indicator light should go out. When this happens....look inside. The element is still bright orange and emitting heat and will continue to raise the temperature in the oven to approximately 325 - 340 degrees. With this noted, you will see the temperature beginning to drop 315, 310, 300, 295, 290, 285 perhaps even 280 or some even lower to 275 and then the indicator lamp will go on indicating the circuit has closed thus turning on the element, Finally there is a variance and no range GAS or ELECTRIC will ever maintain a even 300 degree temperature. The calibration set point is based on the 300 degrees. If your oven light goes off within 20-25 degrees of three hundred degrees, your oven is already calibrated pretty close and I would not attempt to adjust it at all.

Sounds like your oven probe sensor has got issues. Pretty easy to fix, just look inside oven for the probe (small round cyclinder, about a pencil width or smaller, mounted usually in the back top corners), remove the two screws, then slide it out. Some models have the probes where you will have to take the back off to get to them. If your probe is ok, then you might possibly have an issue with your main oven control, which may be computer or knob type. These (especially if computer driven) can be very expensive to fix, and some need calibration. Good luck and let me know if you need any other assistance.