As just one 4"x1.5" round cake pan holds in total approximately 2 cups of batter full, you will want to make a total of approximately 2-3 cups of batter to share between two 4" round cake pans. You only want to fill the cake pans half full to 2/3 full AT MOST.
By the way.....Welcome to Cheftalk!! /img/vbsmilies/smilies/smile.gif
(Also, as this thread is for professional bakers or pastry chefs there is another awesome thread in this forum that us professionals still answer in but is for the home cooks and bakers out there under Cooking Discussions called Baking and Pastries.......please feel free to ask any of your questions there as this thread is limited to professional industry questions. Not to worry, just a heads up as most people miss this at the top of the thread column when they first post /img/vbsmilies/smilies/wink.gif)
Glad you have joined us and remember to take pictures of your lovely baked goods to show off to us as we really like to ooooh and ahhhh over peoples fantastic creations homemade with love or professional made with precision doesn't make a difference because we are all here to create!