How much buttercream do you need?
Enter the cake and get the amount to make, plus the ganache ratio for filling, drips, or under fondant.
Free. No signup needed.The cake
Buttercream
641 g
About 2.8 cups, filled and covered
Or ganache
756 g
Ganache is denser, so the same coat weighs more
Ganache, made up
Chocolate
504 g
Double cream
252 g
Worked from the surface the frosting has to cover, so a 12 in cake gets its own answer rather than one and a half times an 8 in. Make about 10% more than this. Scraping a bowl clean mid-crumb-coat is how cakes end up patchy.
Costing that buttercream is the other half of the job. BakerInbox keeps your recipes and prices together.
Start free trialButtercream and ganache quantities
The amount of frosting a cake takes comes from the surface it has to cover, not from how many people it feeds.
The mistake
A 12 inch cake is not one and a half 8 inch cakes
Frosting covers a surface, and surface grows with the square of the width. An 8 in cake takes about 640 g of buttercream filled and covered. A 12 in of the same height takes closer to 1.25 kg. Scale by the tin number and you run out halfway round the second coat.
Finish
How you finish it changes the amount more than you think
A semi-naked crumb coat uses about half what a smooth finish uses. Building up sharp edges, or laying down a base for fondant, uses about half again more than smooth. Pick the finish first, then make the batch.
Ganache
Ratios are by weight, and they are not interchangeable
Dark chocolate sets firm at two parts chocolate to one part cream, which is why it holds an edge under fondant. Milk and white chocolate are softer, so they need three to one. For a filling or a drip, one to one stays spreadable and pourable.
Practical
Make about 10% more than the number says
Buttercream sticks to the bowl, the spatula, and the scraper. Running out mid crumb coat means a fresh batch at a different temperature and a patchy finish. Better a spare tub in the fridge than a rescue job at midnight.
FAQ
Common questions
How much buttercream do I need for an 8 inch cake?
About 640 g for a three layer 8 in round with a smooth finish, filled and covered. A crumb coat only needs roughly half that.
How much buttercream is that in cups?
A cup of buttercream weighs around 226 g, so 640 g is a little under three cups. The calculator shows both.
What ratio of ganache goes under fondant?
Two parts dark chocolate to one part double cream, by weight. Milk and white chocolate are softer and need three to one to set as firm.
Does ganache weigh more than buttercream for the same cake?
Yes. Ganache is denser, so the same coverage comes out around 18% heavier even though it goes on thinner.
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