Measure the Real Temperature
Oven displays show the temperature the oven is trying to reach, not necessarily the temperature inside. Place an oven thermometer in the centre of the oven, preheat fully, and compare the thermometer reading with the setting after the oven has settled. Check more than once, and check in the centre rather than near the door or the element, where readings swing more.
Note whether the oven is consistently low or high by a similar amount, whether it swings up and down, or whether one side cooks faster than the other. A consistent offset points to a different cause than wild swings, and that detail helps diagnosis.
Preheat, Racks, and Door Seals
Give the oven time to preheat fully before putting food in, and avoid opening the door repeatedly to check: every opening drops the temperature and extends cooking time. Rack position matters too. Food placed very close to an element, or on a rack that blocks airflow, will cook unevenly even in a healthy oven.
Check the door seal and hinges. A door that does not close fully, or a gasket that is torn, flattened, or missing in places, lets heat escape and makes the oven work harder to hold temperature. A worn seal is a straightforward fix on many models.
Sensors, Elements, and Igniters
On electric ovens, a bake element that is visibly damaged, blistered, or only partly glowing, or a temperature sensor that has drifted out of range, are common causes of wrong temperatures. On gas ovens, a weak igniter can delay lighting or cause uneven heat. Thermostats and control boards can also fail, but they should be tested, not guessed at.
Do not work on gas igniters, gas valves, or electrical elements yourself. If you smell gas, leave the home and call your gas utility or 911 from outside. If there is no gas smell, note whether burners light normally and whether the oven lights at all, and call us for a diagnosis.
When Calibration Is, and Is Not, the Answer
Some ovens allow a small temperature offset to be adjusted in the controls. A small, consistent offset can sometimes be corrected that way, following the maker's instructions. A large offset, wild swings, or an oven that will not heat at all is not a calibration problem: it is a part that needs testing.
When you call, tell us the brand and model number, how far off the temperature is, whether the problem is new or gradual, and whether the door closes properly. See our oven and range repair page for what a visit includes, including temperature testing before any part is replaced.