Buttercream Calculator

Classic British buttercream uses a 2:1 ratio of icing sugar to butter by weight. So for every 100g of butter, you need 200g of icing sugar. Add a small amount of milk (about 1 tablespoon per 250g icing sugar) to reach spreading consistency.

For a 20cm (8 inch) round cake with filling and coating, you need approximately 500g of buttercream total — about 150g for the filling between two layers and 350g for the crumb coat and final coat on the outside.

Yes, the butter should be at room temperature (about 20°C) and soft enough to beat easily but not melted or greasy. Cold butter will create a lumpy buttercream, and melted butter will make it too runny. Beat the butter alone first until pale and fluffy before adding the icing sugar.

Add 2-3 tablespoons of cocoa powder per 250g icing sugar, or fold in 100g of melted and cooled dark chocolate per 500g of finished buttercream. Reduce the milk slightly when using melted chocolate as it adds moisture.

Yes, buttercream keeps well in an airtight container in the fridge for up to a week, or frozen for up to 3 months. Bring to room temperature and re-beat before using to restore its fluffy texture.

Grainy buttercream is usually caused by under-beating or using icing sugar that is not fine enough. Beat the buttercream on medium-high speed for at least 3-5 minutes after adding all the icing sugar. Using a stand mixer gives the best results.