What size pan is considered a half a sheet cake???
Grocery store size? A full sheet is 24 X 18 which means a half sheet would be 12X18... I normally make my full sheets with two 12x 18 inch pans.
Sheet Pan sizes
Eighth Sheet Pans 6½ X 9
Quarter Sheet Cakes: 9 x 13 (sometimes (9½X13)
Half Sheet Cakes: 13 x 18
Full Sheet Cakes: 18 x 26
Oops forgot ¾ size 21 X 15