British recipes often list a gas mark for the oven temperature.  This chart should help to convert the temperatures.

225 F = 1/4 Mark
250 F = 1/2 Mark
275 F = 1 Mark
300 F = 2 Marks
325 F = 3 Marks
350 F = 4 Marks
375 F = 5 Marks
400 F = 6 Marks
425 F = 7 Marks
450 F = 8 Marks
475 F = 9 Marks