The difference between sheet cakes and 'regular cakes' is the pan that is used to bake them in. That is, sheet cakes are baked on cake sheets rather than in a pan. Sheet cake pans come in three basic sizes. A full cake sheet pan is 18X26", a half sheet pan is 13X18", and a quarter sheet pan is 9X13" in size. Most sheet pans are between 3/4" to 2" inch tall. Note that these sizes approximate and can vary depending on the manufacturer.