I have to do a wedding cake for 400 guests ,I am doing a red velvet cake with vanilla moussline and the cake is 3 inch high and is 3 tiered. they are square cakes -15, 11 and 7 inch and i am doing an 2 extra 11 inch cake so I wondering if this much cake is enough or should I do some additional servings as well

Hi Salmat!  It looks like you are close with your serving amounts.  My quick calculations show that you would get about 516 sq. inches of cake surface.  Using small portions (3/4” x 2” cut size = top surface area of 1.5 sq. inches) you will get between 300-340 servings (516sq inches/1.5sq inches =344 portions).  I have usually used this portion size and have never had an issue—however, if you want full dessert sized portions, I would suggest more cake.  If it is part of a late lunch (which is how most weddings serve the cake here), I’d say you have enough, especially since all of the cake is the same type and not different flavours—when I’ve made enough cake for the guest list, I’ve often had close to half left and that’s even with the smaller portions.  This is just my experience.  You may want to know more about the guests/eating habits of the community and if there are other desserts served with the cake.  Also, do the bride and groom plan to keep the 7” cake?  If so, you will want more cake!

Good luck with the project and we’d love to see pics!!!

hey thanks for the reply sherrie, this is a made to order cake so i have no clue about the guests and the bride and groom are not keeping any cake , I just know there’s going to be another desert as well so I might just make another 8 inch cake just incase i feel it wont be enough , the cake is due on 29th so I still have time

Wish I had seen this sooner; hope it’s not too late. This is the chart that I have used for years and you get a decent size piece of cake.
DeDe Wilson cake serving chart

Round
4”  4
5”  6
6”  8-10
7”  10-12
8”  12-16
9”  16-22
10”  23-34
12”  36-48
14”  47-66

Popular Tier Combinations
6, 10               30
12, 6   R, 12 H     Under 40
10, 6 S   or R     Under 50
6, 9, 12       60-80
6, 10, 14     78-110
(6) 8, 12, 14       95-130
(6) 9, 12, 14     `  100-136
8, 12         48-64
6, 8, 12, 14     103-140
6, 10, 12, 14     114-158

Sheet Cakes
9 x 13                 12-24       ¼ sheet
12 x 18       24-48       ½ sheet
24 x 36       48 – 96   full sheet
Square
8 x8x2           8
9x9x2         10
10x10x2     16
14x14x2     24