As the name implies, a quarter sheet cake is one-fourth the size of a full sheet cake. According to Baking 911, a quarter sheet cake serves approximately 12 to 20 people.
How Sheet Cakes Are Baked
Sheet cakes are baked in large flat pans called jelly roll or sheet pans, which come in both commercial baking size and home baking size. Most home ovens will hold only up to a 17-inch by 14-inch pan.
Commercial Size Pans
Commercial quarter sheet cakes measure 13 inches by 9 inches by 1 inch, or 12 inches by 8 inches by 2 or 3 inches. Some measure 10 1/2 inches by 15 1/2 inches by 2 or 3 inches.
Home Size Pans
A home-size jelly roll or sheet cake pan is roughly equivalent to a commercial quarter-size sheet cake, measuring either 10 1/2 inches by 15 1/2 inches by 1 inch (10 cups), or 12 1/2 inches by 17 1/2 inches by 1 inch (12 cups).
How To Test a Pan's Volume
You can test the volume of a pan at home by filling the pan to the rim with water, then pouring the water into a measuring cup. Remember that even though a quarter sheet cake pan holds 12 cups of liquid, you will not place that much batter in it.
How To Measure a Pan
Measure from the inside edges of the pan's sides. Place the measuring stick against the pan's bottom and measure up to within 1/4 inch of the pan's top for the depth.