Recipe

My favourite sponge cake recipe (and how I use a sponge cake calculator to scale it)

This is the sponge I trust for birthdays and family bakes. It is light, reliable, and easy to scale with a simple sponge cake calculator when I need a different round cake size.

For ingredient scaling, I now use this sponge cake calculator. It starts from this exact base recipe: an 8 inch, 2-layer sponge cake, but it is equally useful if you want to scale it for a 3 or 4 layer cake, a larger tin, or a celebration cake with extra height.

If you are making a rainbow cake, you will usually need at least 4 layers, and a larger tin or taller stack will change the batter quantities quite a bit. That is exactly the sort of situation this calculator helps with.

Base recipe (8 inch / 20cm, 2 layers)

Sponge ingredients

225g unsalted butter, very soft
225g caster sugar
4 large eggs (room temperature)
225g self-raising flour
1 1/2 tsp baking powder
1/2 tsp fine salt
1 tsp vanilla extract
2 to 3 tbsp whole milk

Filling

4 tbsp smooth strawberry or raspberry jam
200ml double cream
1 tbsp icing sugar (for cream)

Finish

Icing sugar for dusting

Method

Preheat to 170C fan / 180C conventional. Grease and line tins fully (base and sides).
Cream butter and sugar for 5 to 7 minutes until very pale, fluffy, and increased in volume.
Beat eggs in a jug first, then add slowly over 1 to 2 minutes while mixing.
Sift flour, baking powder, and salt. Fold in gently with a spatula.
Stir in vanilla and 2 tbsp milk. Batter should drop slowly from a spoon. Add another tbsp milk if needed.
Divide evenly between tins and level gently. Bake 25 to 30 minutes until golden, springy, and a skewer comes out clean.

Why this method works so well

The biggest difference-maker is the intensive creaming step. Spending a full 5 to 7 minutes on butter and sugar builds most of the lift before the cake even goes in the oven.

Adding eggs slowly also protects that structure. If the mixture curdles slightly, a spoon of flour usually brings it back together.

Scaling this recipe with a sponge cake calculator

This recipe is written for an 8 inch 2-layer sponge, but not every order or celebration needs that exact size. The sponge cake calculator lets you keep the same recipe style while adjusting amounts for larger or smaller round cakes and different layer counts.

If you also need frosting quantities after resizing the sponge, use the Quick Round Cake Buttercream Calculator or the Custom Shape Cake Buttercream Calculator.