The temperature control knobs of home gas ovens manufactured in Great Britain were often marked with a sequence of numerals, the purpose being to enable the cook to return to a previously satisfactory setting, and not necessarily to indicate a precise temperature. In a way, that was more honest than the North American practice of marking such knobs in degrees, because of the great variability from oven to oven, and because knob settings corresponded only roughly with temperatures (which is still usually the case, even with ovens whose knobs are marked in degrees).
Over time the controls improved and around the middle of the 20th century gas mark numbers began to appear in recipes along side or even in place of the verbal descriptions long used by cooks.
Similar scales were used in, for example, France, which are are not identical to the British scale. So, in using this table, be sure the source of the gas mark number is a British recipe.
The Fahrenheit and Celsius temperatures have been rounded off at the intervals conventionally used by cooks.
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Last revised: 29 August 2008.