How much buttercream do you need?
Too little frosting ruins a cake and too much wastes butter and sugar. This buttercream quantity calculator works out the amount from the size of the cake: the surface that has to be covered, the thickness of the outer coat, an optional thin crumb coat and the filling between the layers. For cupcakes it multiplies the number by the amount each topping style needs.
The answer comes as millilitres, US cups and grams, and the recipe table scales a standard American, Swiss meringue or cream cheese recipe to that exact weight, so you can weigh everything out in one go. It all runs in your browser.
How to use the Buttercream & Frosting Quantity Calculator
- Choose a layer cake or cupcakes and the type of frosting.
- For a cake, enter the shape, width, total height and number of layers. Adjust the coat thicknesses if you like a thicker or thinner finish.
- For cupcakes, enter how many and the style of topping.
- Keep a 10 per cent extra allowance for piping and waste, or raise it for borders and heavy decoration, then weigh out the scaled recipe.
Buttercream & Frosting Quantity Calculator features
Real geometry
Top and side areas for round and square cakes, in inches or centimetres.
Filling and crumb coat
Layers and a thin crumb coat are counted, not guessed.
Cupcake styles
Mini, knife-spread and piped swirls at 15 to 75 ml each.
Scaled recipes
Three frostings given as percentages and converted to grams for your batch.
How the amount is calculated
Frosting volume is surface area times thickness. The top of a round cake is π × radius², the side is the circumference times the height, and the base is left out because it sits on the board. An 8-inch round cake that is 4 inches high has about 970 cm² to cover. A 6 mm outer coat needs about 580 ml, a 2 mm crumb coat about 195 ml, and one layer of 5 mm filling about 160 ml, for roughly 940 ml before the allowance. With 10 per cent extra that is just over four US cups, which agrees with the common advice of four cups or so for a two-layer 8-inch cake.
Weight depends on how much air is beaten in. American buttercream averages about 0.95 g per ml, whipped meringue buttercream about 0.85, and cream cheese frosting about 1.0. Those are typical figures, so expect a few per cent either way.
Tips for planning
- Make extra, not less. It keeps in the fridge for a week and freezes well. A ten per cent allowance covers most piping; heavy borders and rosettes can take 30 to 50 per cent more.
- Tall or wide cakes. The side area grows with height, so a 6-inch cake that is 6 inches tall needs nearly as much as a wider, shorter one.
- Smooth sides. A smooth finish uses less than a textured or swirled one. A crumb coat uses a little, but it makes the final coat neater.
- Temperature. Cream cheese and meringue frostings soften quickly in a warm room, so chill the finished cake and keep it cool for serving.
Related baking tools
Covering a cake in fondant instead? Use the fondant calculator. For a chocolate finish, the ganache ratio calculator gives the cream and chocolate for glaze, drip or piping. To bake the same cake in a different tin, see the cake pan converter, and to scale any recipe use the recipe scaler.
Buttercream & Frosting Quantity Calculator FAQ
How much buttercream do I need for an 8-inch cake?
About four US cups (roughly 950 ml, or 900 g) for a two-layer, 4-inch-high cake with filling, a crumb coat and a smooth outer coat. The calculator adds 10 per cent for piping and waste.
How much frosting for 12 cupcakes?
About 360 ml (1½ cups) for 12 knife-spread cupcakes, 600 ml (2½ cups) for medium piped swirls and 900 ml (3¾ cups) for tall swirls, before the extra allowance.
What is a crumb coat and do I need one?
A thin first layer of frosting that traps crumbs, chilled before the final coat. It is optional, but it makes a smooth finish much easier and adds roughly 20 per cent to the frosting needed.
How do I scale a buttercream recipe?
Use the percentages in the table: weigh the total you need, then take each ingredient as its share. American buttercream is about 30 per cent butter and 63 per cent icing sugar.
Why does the UK sometimes say icing and the US frosting?
They are the same thing for this purpose. This calculator uses both words so a search for either one finds it.
Is the answer exact?
No. Thickness varies with technique, and piping, textures and decorations change the total. Treat it as a well-grounded estimate and keep a little extra.