According to Cadco-ltd.com, as a rule of thumb: Bake for the amount of time that the conventional recipe calls for, but reduce the temperature of the oven by 25-30 degrees F.
In this case, if you're baking at 350 degrees for 40 minutes, you must bake it at 325 degrees for 40 minutes as well.
What are the baking times for different sized cake pans? Visit Baking.about.com to learn more.
Learn how to convert Conventional Oven times and temperatures to Convection Oven settings at Had2know.com.
Try these foolproof baking tips and techniques, brought to you from the Real Simple test kitchen.