Cakes are normally cut into 'Finger Portions' (1x1 inch square), or occasionally 'Dessert/Coffee Portions' (1x2 inch long). The choice is greatly up to you. You should, however, check with whoever will be cutting and serving your cake – such as your venue – just in case they have a preferred method.
All of my cake tiers are approximately 4 inches high, meaning you get a satisfying amount of cake in each portion (whichever size you decide to cut).
Below you can find a rough portion guide for a few different cake sizes. Many varying factors can affect the number of portions, such as the accuracy of the person cutting, and slight variations in cake size, so allow for some discrepancy. These are only a few of the sizes I can create, so don't worry if you don't see the exact numbers you are hoping for. Contact me, and I'll be more than happy to advise which size cake would be best for your wedding or celebration.
ROUGH PORTION GUIDE
Small Two Tier: 20-36 finger portions
Small Three Tier: 52-80 finger portions
Small Four Tier: 112-148 finger portions
Five Tier: 200-260 finger portions