We are often asked things like 'How much birthday cake do we need to feed 50 guests?' or 'How many tiers do we need in our wedding cake?' and it's one of those questions that depend on a lot of different variables. Here are a few points to think about, and which your cake maker should go over with you, in order to get the right amount.
The point in the celebrations that the cake is served can affect how much cake you need. For instance, if you serve your wedding cake directly after your wedding breakfast then it's likely that people will only want a small taster so you will need less cake. Whereas if you keep the cutting of the cake to share with your evening guests you might want more so you can serve it as the sweet element of your evening food. The same applies to birthday cakes - if your having a big meal out you'll want to allow less than you would if you were having a barbeque in the garden.
Seriously, I once had a groom tell me that he didn't get a slice of his wedding cake but one of his rugby mates happily told him 'that cake was awesome, I had a slice of all four flavours'!! You know your guests best so if you have lots of major cake fans maybe ask your cake maker to allow a bit extra!
If it's a wedding cake you may want to follow the tradition of keeping the top tier for the christening of your first child in which case it will need to be discounted from the portion count for the day.
If, like lots of our lovely clients, you have an unusual wedding cake or birthday cake then you may want to allow a few extra slices as there can be a big variation in the depth of the cake, and therefore the portions, at different points in the design.
Ultimately your cake maker shoud ask all the right questions to make sure you have enough cake to feed your guests but if you'd like to work it out for yourself below is a handy graphic we've put together for different sized tiers and portions sizes.