Sheet Cake Question...

Hi All,

Okay so I get a little confused sometimes because on some of the websites I see the following sheet cakes are described:

9x13 - quarter sheet

11x15 - third sheet

12x18 - half sheet

18x24 - full sheet

BUT on other sites the following sizes are used:

9x13 - half sheet

12x18 - full sheet

And the confusion continues! So my question is - what standards do you guys used? 

I have a 9x13 pan, an 11x15 pan and a 12x18 pan, so I want to make sure I use the appropriate label for each pan size! 

Many thanks all!