Frosting Calculator: How Much Frosting Do I Need?

About 4½ to 5 cups, or roughly 1,150 g of American buttercream, if you want a crumb coat, filling between the layers, a full outside coat and a simple piped border. Drop the border and it is closer to 4 cups. Add heavy piping over the whole surface and it climbs past 6.

Most published charts say 4 to 5 cups without telling you which of those jobs they counted, which is exactly why bakers run out. The breakdown in the calculator above shows where each cup goes, so you can see immediately whether your plan fits the batch you are making.

About 1½ cups if you are spreading it on with a knife, and about 3 cups if you are piping a tall bakery style swirl. That is a genuine doubling, and it is the most common frosting miscalculation there is.

A knife-spread cupcake takes roughly 2 tablespoons. A piped swirl takes 3 to 4 tablespoons because the swirl is a solid cone of frosting standing above the cake, and a big open star tip makes it bigger still. Set the calculator to cupcakes and match the decoration level to what you actually plan to do.

For anything with a visible finish, yes, and it is cheaper than you think. A crumb coat is a deliberately thin scraping of frosting that traps loose crumbs against the cake so they cannot drag into your final coat and speckle it. On a 9 inch two-layer cake it costs about 0.6 of a cup, which is a little over one eighth of the total.

Chill it for 20 to 30 minutes until it is firm to the touch before the outside coat goes on. A crumb coat that is still soft simply mixes into the top coat and you have done the work for nothing. You can skip it entirely for a rustic or naked finish, or where the frosting is dark enough to hide crumbs, such as chocolate ganache on a chocolate cake.

Roughly 1 cup for a 9 inch join, ¾ cup for 8 inch and a scant ½ cup for 6 inch, at a normal filling thickness of just over a fifth of an inch. A three layer cake has two joins, so double it.

Go much thicker than that and the weight of the upper layers squeezes the filling out at the sides, which is what causes the bulge you then have to scrape off and hide. If you want a thick filling, pipe a dam of stiff frosting around the edge first and fill inside it. That is also how you use a loose filling like curd or jam without it escaping.

It depends entirely on the recipe you mean by a batch. The standard American buttercream in this tool, made with 1 cup of butter and 4 cups of powdered sugar, yields about 3 cups. That covers a 6 inch or 8 inch two-layer cake comfortably and falls short on a 9 inch one.

The scaled ingredient list in the calculator solves this by giving you the exact quantities for your cake rather than a multiple of somebody else's batch. If the numbers land awkwardly, round up. Nobody has ever regretted having a spare cup of buttercream in the fridge.

Roughly 670 g for an 8 inch two-layer cake and 780 g for a 9 inch, rolled to about an eighth of an inch. Published figures for this run anywhere from 600 g to 1 kg for a 9 inch cake, because how much skirt you trim off depends entirely on how neatly you roll, so buy the next packet size up. Set the frosting type to rolled fondant above for your own tin.

Two things to remember. First, you roll a circle far wider than the cake, because it has to reach across the top and down all the sides, and you then trim off a skirt you cannot reuse cleanly; that trim is already included here. Second, fondant is a covering, not a frosting: it needs a layer of buttercream or set ganache under it to stick to and to smooth out the shape of the cake. Pick rolled fondant in the calculator and it drops the crumb coat and filling out of the fondant weight, then tells you separately how much buttercream to make for underneath.

Yes, and it is one of the few genuinely stress-reducing things you can do before a cake. American buttercream, Swiss and Italian meringue buttercreams all keep about a week refrigerated and up to three months frozen in an airtight container. Ganache keeps two weeks refrigerated.

The critical step is bringing it back. Let it come fully to room temperature, then rewhip it, which takes several minutes and will look curdled and broken partway through. Keep going; it comes back together. Cream cheese frosting and whipped cream are the exceptions: both are best made the day you use them and neither freezes well.

Because almost all of a cake's surface is its sides, and the sides grow directly with height. A 9 inch cake has 64 square inches of top no matter how tall it is, but a 4 inch tall one has 113 square inches of side and a 6 inch tall one has 170. Adding a third layer therefore adds far more frosting than people expect, and it also adds another filling join.

This is why frosting charts that only list pan diameters mislead you. The calculator above asks for your layer count and layer thickness for exactly this reason, and you can watch the total move as you change them.

About 4 cups, or roughly 960 g of American buttercream, for a crumb coat, filling, outside coat and a simple piped border with 2 inch layers. With a smooth finish and no border it is closer to 3½ cups, and with piping over the whole cake about 5½ cups.

For a 9 x 13 inch cake frosted in the pan, top only, plan on about 2 cups for a smooth coat and about 2½ cups with a piped border. If you turn it out and frost the sides too, make about 4¼ cups. One batch of American buttercream covers the top with room to spare.

About 3 cups spread with a knife, about 4½ cups for a small piped swirl, and about 6 cups for a tall bakery swirl. That means one batch of American buttercream frosts two dozen cupcakes only if you spread it; for piped swirls make two batches.

For a 12 x 18 inch half sheet frosted top only, about 3¾ cups smooth and about 4½ cups with a piped border. Heavy piping or writing across the top pushes it to roughly 6¾ cups. Pan sizes vary a little, so round up for a 13 x 18 inch pan.

About 3¾ cups for a 6 inch, 5¾ cups for an 8 inch and 6¾ cups for a 9 inch three layer cake with 2 inch layers and a simple border. A third layer adds both another filling join and taller sides, so it needs nearly half again what a two-layer cake does.

A 2 lb bag holds about 907 g, which is enough for just under two batches of the American buttercream in this calculator (480 g of sugar each). That works out to roughly 5roughly 5½ cups of frostingfrac12; to 5¾ cups of frosting, enough for a 9 inch two-layer cake with a border, but not quite enough for a 9 inch three layer cake.