- oven temperature is set according to four different scales, three quantitative, i.e. Fahrenheit °F, Centigrade °C, or gas mark GM, and one qualitative, i.e. cool <120°C, slow 120°C, moderate 180°C, hot 220°C and very hot 250°C. As a rule of thumb °F are twice °C. This is exactly so at 144 °C; above this °F are slightly less than double and below slightly more than double.