How do I check my oven temperature and fix an inaccurate oven?
Most ovens are wrong by 20°C or more — how to find out by how much and what to do about it.
- Difficulty
- beginner
- Time
- 20 min
- Read
- 2 min
Short answer
Put an oven thermometer in the middle and compare with the dial after it has fully preheated. Most domestic ovens are out by 20°C or more, and knowing your offset explains a great deal of inconsistent baking.
Recipes assume an accurate oven and very few are. An oven running 25°C cool explains dense bread, pale pastry and undercooked centres simultaneously — and it costs almost nothing to find out.
What you'll need
- Oven thermometer
- Second thermometer (optional)
Step by step
- Buy an oven thermometer.A few pounds. The dial on the oven reads what the thermostat is asking for, not what is happening inside.
- Place it in the centre and preheat fully.Middle shelf, middle of the oven. Preheat for at least 20 minutes — most ovens signal ready long before they are stable.
- Compare the reading with the dial.Do this at two or three temperatures — 150°C, 180°C and 220°C. The error is often different at different settings.
- Write the offset somewhere.On a card inside a cupboard door. "Runs 20°C cool" is all you need, and you will not remember it otherwise.
- Check for hot and cold spots.Move the thermometer around, or bake a tray of scones and see which brown first. Almost every oven has them.
- Rotate trays partway through.The simplest compensation for uneven heat, and it costs nothing.
- Adjust the recipe, not the oven.If it runs 20°C cool, set it 20°C higher. Most ovens can also be recalibrated in the settings — check the manual before calling anyone.
- Get it looked at if it is wildly out or unstable.More than about 30°C, or a temperature that swings, usually means a failing thermostat or element. That is a repair rather than a workaround.
Tips
- Fan ovens usually need about 20°C less than a conventional recipe states, and this is separate from any inaccuracy.
- Leave the thermometer in permanently. It becomes something you glance at rather than a project.
- Opening the door drops the temperature sharply and it takes several minutes to recover. Use the light instead.
Questions people ask
How accurate are domestic ovens?
Frequently out by 20°C or more, and often different at different settings. An inexpensive oven thermometer tells you your own oven's offset.
Do I need to reduce the temperature for a fan oven?
Usually by about 20°C from a conventional recipe. That is separate from any inaccuracy, so check both.