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 short answer
A three layer 8 inch (20cm) round takes about 640 g of buttercream for a smooth finish, or about 460 g for a crumb coat alone. A dozen cupcakes with a standard swirl takes about 460 g, and 24 about 915 g. Enter your cake below for the exact amount and what to buy.
How much buttercream do you need?
BakerInbox
The cake
Adjust my coverage rates
Buttercream
705 g
About 3.1 cups, 10% extra included
Or ganache
832 g
Ganache is denser, so the same coat weighs more
Ganache, made up
Chocolate
555 g
Double cream
277 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. The 10% extra is already in the numbers above, so that is the amount to weigh out.
Costing that buttercream is the other half of the job. BakerInbox keeps your recipes and prices together.
Start free trialButtercream by cake and by batch
| Round cake, 3 layers | Crumb coat | Smooth finish | Sharp edges |
|---|---|---|---|
| 6 in | 285 g10.0 oz | 405 g14 oz | 510 g1 lb 2 oz |
| 7 in | 365 g13 oz | 520 g1 lb 2 oz | 640 g1 lb 7 oz |
| 8 in | 460 g1 lb | 640 g1 lb 7 oz | 790 g1 lb 12 oz |
| 9 in | 565 g1 lb 4 oz | 775 g1 lb 11 oz | 950 g2 lb 1 oz |
| 10 in | 680 g1 lb 8 oz | 925 g2 lb 1 oz | 1.12 kg2 lb 8 oz |
| 12 in | 945 g2 lb 1 oz | 1.26 kg2 lb 12 oz | 1.51 kg3 lb 5 oz |
Filled and covered, three layers about 4.5 in tall. Make roughly 10% over the number: a fair amount stays on the bowl, the spatula and the scraper.
Cupcakes, by the batch
| Cupcakes | Spread flat | Standard swirl | Tall swirl | Butter and icing sugar |
|---|---|---|---|---|
| 12 | 320 g11 oz | 460 g1 lb | 670 g1 lb 8 oz | 155 g and 305 g |
| 24 | 640 g1 lb 7 oz | 915 g2 lb | 1.34 kg2 lb 15 oz | 305 g and 610 g |
| 36 | 965 g2 lb 2 oz | 1.38 kg3 lb 1 oz | 2.02 kg4 lb 7 oz | 460 g and 915 g |
| 48 | 1.28 kg2 lb 13 oz | 1.83 kg4 lb 1 oz | 2.69 kg5 lb 15 oz | 610 g and 1.22 kg |
| 50 | 1.34 kg2 lb 15 oz | 1.91 kg4 lb 3 oz | 2.80 kg6 lb 3 oz | 635 g and 1.27 kg |
Worked on a standard 2.5 in case. The last column is what a standard swirl takes at one part butter to two parts icing sugar, the UK ratio the calculator uses.
Made with BakerInbox. Free cake tools at bakerinbox.com/tools
Buttercream 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.
How much buttercream for 12 cupcakes?
About 460 g for a standard piped swirl on a dozen, which is roughly 155 g of butter to 305 g of icing sugar. A flat spread top takes closer to 320 g, a tall show swirl nearer 670 g.
How much buttercream for 24 cupcakes?
About 915 g for a standard swirl on two dozen, from roughly 305 g of butter and 610 g of icing sugar. Double it again for 48. The table above runs from 12 up to 50.
How much buttercream to ice a 20 cm cake?
A 20 cm tin is an 8 in tin, so about 640 g for three layers filled and coated. UK and European tins are sold in centimetres and the conversion is not exact: 20 cm is 7.9 in, and it is used as an 8 in.
What size cake will 500 g of buttercream cover?
Roughly a 7 in cake with three layers, or an 8 in if you keep the outside coat thin. For cupcakes, 500 g is about 13 at a standard swirl. Enter your cake above for the exact figure rather than working back from a batch you have already made.
How much frosting for a 9 inch cake in ounces?
About 1 lb 11 oz for a three layer 9 inch pan, filled and smooth coated, or 1 lb 4 oz for a crumb coat alone. An 8 inch takes about 1 lb 7 oz. Switch the calculator to US measurements and every figure comes back in ounces and pounds, with the butter also given in sticks.
What is icing sugar called in the US?
Powdered sugar, or confectioners sugar. They are the same thing and weigh the same, so any amount here works unchanged. Double cream is heavy cream, a cake tin is a cake pan, and caster sugar is superfine sugar, though most US recipes still call it caster.
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