From giant birthday cakes to tiny cupcakes, all cakes are made by getting the ratio of ingredients just right.
Take a basic sponge recipe:
200 g of sugar, 200 g of flour, 200 g of butter, 4 eggs, 1 teaspoon of baking powder and 30 ml of milk.
This simple, standard recipe can be used to calculate the ratio of ingredients needed to make any size of sponge cake.
The ingredients involved in making a sponge can be written like this.
200g sugar : 200g flour : 200g butter : 4 eggs : 1tsp baking powder : 30ml milk
If you look at the ratio of sugar to flour, this can be simplified by dividing both sides of the ratio by the highest possible common factor, in this case 200.
This gives a sugar to flour ratio of 1 to 1.
The highest common factor between 4 eggs to 30ml of milk is 2, giving an egg to milk ratio of 2 to 15.
Because ratios are often expressed in terms of 1, 2 to 15 can be divided further to give the ratio 1 to 7.5.
As long as all the ingredients are multiplied by the same amount, these ratios will remain the same and any size of cake can be made.
If you want a cake half the size, multiply the ingredients by a half.
If you want a cake 100 times larger, multiply the ingredients by 100.
As long as you understand the ratios involved, the size of cake you make is really up to you.