Gas marks has the "let's guess" conversion. It is a risky approach; the thing is that we have always bake like that so it is no bother at all. Cakes could be done at X° Celsius or at a "moderate" during 45 minutes. I also have an old fashion stove that need to be heat by wood. I burn everything I try to bake there, but my husband can bake and cook pretty well there.