How many portions of wedding cake do you actually need?

It's not just the number, but the size of the portion. If it's for guests to take home then the portion size is usually smaller than if you were to have cake for dessert. Also, not everyone likes cake anyway (crazy people!) so I wouldn't cater for every guest. If you're expecting 150 guests I would cater for about 120 and you'll more than likely still be left with some at the end.

The cake is to take home/be handed round later in the evening, rather than to be served as pudding. I know what you mean about not everyone wanting some. I went to four weddings last year and I think I only ate the cake at one of them (it was amazing though, red velvet!).

Sorry it is potato quality but this seems quite useful. I'd go for 120 portions if you are expecting 150 people.

But if you was guest 121 who wanted cake and guest 120 had took said cake, wouldn't you be disappointed? Or auntie may deciding cousin sue (who wasn't invited) would love some cake taking home, and hey look there's loooooads so auntie may takes several peices. Imo and maybe it was me bring cautious I believe you should cover one per item to each guest plus 10% I know my cake was an important element so I over catered

If it doesn't make too much difference to the cost and you're ok with binning some I suppose you could just cater for the full 150. I'm just going off of what several bakers told us when we were making inquiries for our cake and it made sense to me.

My sister had cupcakes for her wedding cake and she did one for everyone (about 90 people). My fiancé and I had a couple each as it was nearly the end of the night and it was clear the cakes weren't going anywhere. My sister later told me that only 30-40 of the cakes went meaning over half went to waste. This would have been the case if she'd only catered for 80 but it would have still meant 10 less in the bin!

Our cake will cater for about 120 people and we're expecting to invite 100-120 (we think)

In your case, I would make a cake for 150 people. I think the people who take more than their share will balance out the people who don't want any

I tend to use this guide when working out serving sizes

We have 111 during the day and 30-40 extra in the evening. Our cake works out at 176 portions (oops)... it's because our main cake is chocolate with chocolate ganache, and then I have bars of lemon sponge, plain sponge and fruit cake to cover all bases. The cake will get eaten at some point, even if it's with coffee the following morning.

Always better to have too much than not enough and look too tight to buy enough cake

Hmmmm, I would never consider myself "tight" and my other half would certainly argue that I am the exact opposite of tight and wishes I was a bit more frugal!

The numbers that I have suggested and will go by myself are based on the opinions of several bakers who do this week in week out. Being as it is their business, it would make more sense for them to oversell but every baker advised less portions than the number of people estimated to attend. We will also be having a candy cart with cookies and brownies in the evening so there will be plenty to go around for those with a sweet tooth.

The amount of cake left at my sisters wedding was criminal, and I don't want to be left with 40 portions of cake to eat the next day as much as I love cake I think I would be sick, haha!

I wasn't suggesting you were tight. You asked a question and I gave my opinion... I would be mortified if there wasn't enough cake to go round everyone that wanted some. If there is lots leftover I will just send some home with everyone in the morning and have some with coffee as we did at my sister in laws wedding. I've also asked that the venue keep a tier whole if it's not required so we can take it home and freeze it. My friends just defrosted theirs and had it on their first anniversary.

I have honestly never had cake at a wedding and ive heard from many friend in catering that the staff often eat it or it just ends up in the bin with only a token amount being kept

but then it depends on your group of friends ive seen (on tv only mind you) places get mobbed for the cake before... one show about extravigant cakes even had people climing up furniture to steal the decerations on top tiers ?

I think this is one of those times when a bit of professional advice would be wonderful. Knowing all the facts about your wedding would really help, for instance if you are having other food served at the same time as the cake comes out etc etc

You could ask at the venue, or ring a cake maker & ask. I really don't mind if people ask me photography related questions about their wedding day, even if the couple asking aren't going to book me for their photography.

This is a great diagram, much more straight forward than others I've seen. Going back to the OPs question, I think you are better off over catering than under. Particularly if you are having it out in the evening, say as part of the buffet. I don't think I've ever taken a piece of cake home in my life, but if it's out for people to pick at I would probably have more than one piece. Could you get your friend to make your cake as planned, but have a spare cutting bar that you could have brought out if stocks are running low? M&S do quite a few varieties. It would be fairly cheap so if you don't end up using it, you could always freeze it or take it in to work or something.