I have a client that doesn't seem to under stand that a 12" circle or square cake will feed 30 people. How do I explain to her is a nice way that a 12" cake will definitely feed 30 people. I'm thinking she wants to cut the cake like a pie instead of the way Wilton has showed me.
AThere are charts you can reference online.
print a picture of a cake cutting chart.
AAlso, remember that a 12"'ruler or flat piece of paper looks much smaller than a layered cake. Use photos or cake pans. I love have dummies for this exact reason.
Wilton slices are very small and generally for weddings. Normally, people at a birthday party want a bigger piece of cake. You should explain how small the Wilton pieces are and show her a diagram of how the cake should be cut. Once your customer sees how small the cake slices would be, she may end up ordering a bigger cake and paying the difference. If I were having a birthday party I think I would rather have a little cake left over than not having enough cake for everyone.
AIs she worried she won't have enough or questioning your pricing method? You can let her know that it's the industry standard size for pricing, but if she's concerned she won't have enough cake she's welcome to order more.