Welcome to the Cake Decorators Q&A
What size of tin should I use to feed 70 people for a book shaped sponge cake please?
A 12" square sponge cake will give 72 1" x 2" portions. However, you should also take into consideration any reduction in size due to carving. You could make the serving smaller which would give you more. Remember that not everyone eats cake so this size may well be sufficient.
The portions calculator will help you decide the size cake you might like to bake.
Select the portions calculator.
Hope the calculator helps. Please post back if you need help or information.
Thank you so much. I can make it deeper and by time I carve, hopefully be sufficient.
That's great. Glad you can sort it out without having to bake an additional cutting cake. I was going to suggest making the cake deeper, you're already on it! 🙂 Hope all goes well.