when you go to a bakery and ask for a 1/2 sheet cake, 1/4 sheet...etc..what size are you actually getting? I used to get a 1/2 sheet cake 1/2 white and 1/2 chocolate for my kids birthdays. Now that I'm trying to make their cakes I cannot figure out which size pans to use to get the same thing. Thank you for your help in advance, I know this probably seems like a weird question.

No, it's not a weird question. But it's an excellent example of why I say I refuse to use the terms "half" or "quarter" in reference to sheet sizes. Because even the person ordering the cake has no idea what size cake they are ordering. The general public uses the terms because "that's what everyone says" but they've no idea how big the cake is that they've just committed to paying for.

Had a guy ask me for a price on a FULL sheet cake. I asked him "how many people do you need it to serve?" He tells me ten. TEN!!!! So I ask him, "So why do you want to pay for cake for 100 if you're only having 10 people over?"

Most people, when they ask "How much is a half sheet?", and when I ask them "I don't know ... how big a cake IS that?", they will respond that they have no idea. I'm astounded by this. Someone just asked for a price for a specific item and they've NO IDEA what it is they just ordered. Good god I could sell them anything and they'd have no idea if I was giving them a deal or if I was stealing their money.

In general.....

Full sheet is 18x24 or 18x26. Serves approx 100.
Half sheet is 18x12. Serves approx 50.
Some refer to the 11x15 as a "one-third" sheet cake. Serves 35.
Quarter sheet is 9x12 or 9x13. (Not sure what this serves 'coz I don't make cakes this small.)

But your best bet, when someone asks for a "half" sheet, is just to ask them how many they need to feed and then figure out what they really need.