Free Oven Temperature Conversion calculator with clear step-by-step results.
Converts a recipe temperature between oven types and then corrects for your own oven's measured error. Everything is normalised to a conventional-oven equivalent first, adjusted by 20 C for fan, and finally offset by the calibration error you measured with an oven thermometer.
Fan conversion
A fan oven runs about 20 C hotter than a conventional oven at the same dial setting
Dial setting
Dial = required temperature - measured calibration error
Put an oven thermometer in the centre, set the dial to 180 C, and let it cycle for twenty minutes. The difference between reading and dial is the offset - negative if the oven runs cool.
If the oven runs 8 C cool, you must set the dial 8 C higher to reach the real target. Subtracting a negative offset does exactly that.