There is a trick to determining the answer. Measure with water.
To determine how much batter a pan will hold use a measuring cup and pour water in the pan until it is filled to the brim. Keep in mind that you will want to fill pans that are 1" or 2" deep 1/2 full of batter. So, here you will need to subtract 1/2 from the total amount to determine the capacity. But with pans that are 3" or 4" deep the batter needs to be 2/3 full in the pan. So on deeper pans, subtract 1/3 from the total amount of water in the pan.
Now check the Cake Batter Capacity Chart using the original pan's dimensions and volume for a substitution. It's easiest to compare with a pan that has the same depth, so you won't have to adjust the baking time.
For example: You could substitute a PRD-103 (10" x 3" round pan) which holds 8 cups of batter for a PSQ-10103 (10" x 10" x 3" square pan) which holds 8 3/4 cups of batter and keep the baking time the same.
If the substituted pan is shallower than in the original recipe, you will need to shorten the baking time and raise the temperature of the oven slightly (25 F). If the substituted pan is deeper than in the original recipe, the batter will take longer to cook. You will need to lengthen the baking time and lower the temperature (25 F) slightly. Remember the rule for larger, deeper pans..."Bake Low and Slow".