Cake mix v tin size

[user1496521049]

I am making a 9" cake using a Betty cocker mix. On the mix it states to use 2 8" tins. Does anyone know if there will be much difference in height if I use a 9" instead? I am using 9" as it will be part of a tiered cake

Well, naturally the volume stays the same, so if the diameter is larger then the height/depth has to be lower, unless you are increasing the quantity.