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In this guide
What Is Gas Mark?
Gas Mark is a temperature scale used on gas ovens in the UK and Ireland, standardised in the early twentieth century as a numbered scale from ¼ to 9. It is not linear like Celsius: each full mark above Gas Mark 1 (140°C) adds roughly 14°C.
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Enter any temperature below to see its equivalent across all four scales, including the fan-oven adjustment.
[kc_calc_oven]Gas Mark and Fan Ovens
Fan ovens run hotter than their dial suggests, so the standard adjustment is to reduce the conventional temperature by 20°C (or 25°F). Gas Mark 4 (180°C conventional) becomes 160°C fan; Gas Mark 6 (200°C conventional) becomes 180°C fan.
Practical Tips for Gas-Oven Baking
Gas ovens typically have a hot spot near the flame, so rotating trays halfway through baking helps even browning. An oven thermometer is worthwhile, since dial markings can drift 10–20°C from the true temperature over time.