How much filling does a cake need?
Pick the filling, the tin, and the number of layers. Get the weight to make, and the dam to pipe.
Free. No signup needed.The short answer
A three layer 8 inch round has two gaps, not three, and takes about 310 g of buttercream or 345 g of jam to fill them. Jam, curd and cream also need about 90 g of stiff buttercream piped as a dam round each layer, which the calculator gives on its own line.
How much filling does a cake need?
BakerInbox
The cake to fill
What goes between them
Firm enough to hold itself. No dam needed.
Filling to make
308 g
Buttercream, 2 gaps at 5 mm
Between each layer
154 g
Spread level, right to the edge
Gaps to fill
2 gaps
Layers minus one, always
Worked from one layer surface, the thickness you spread, and the gaps between them, so a wider cake or an extra sponge gets its own answer. A Victoria sandwich smear of jam is nearer 3 mm, and 4 to 5 mm is a generous celebration fill. Jam, curd and cream each need a dam as well: a ring of stiff buttercream piped just inside the edge, mixed before the filling goes anywhere near the cake.
Filling sorted. BakerInbox keeps the recipe, the quote, and the order in one place.
Start free trialFilling per tin size, three layers
| Cake size | Buttercream (5 mm) | Jam or conserve (4 mm) | Lemon or fruit curd (4 mm) | Ganache (5 mm) |
|---|---|---|---|---|
| 6 in | 173 g | 194 g | 166 g | 215 g |
| 7 in | 236 g | 264 g | 226 g | 293 g |
| 8 in | 308 g | 345 g | 296 g | 383 g |
| 9 in | 390 g | 437 g | 374 g | 484 g |
| 10 in | 481 g | 539 g | 462 g | 598 g |
| 12 in | 693 g | 776 g | 665 g | 861 g |
Three layers, so two gaps. A four layer cake of the same size takes half as much again. Each filling is shown at the thickness it is normally spread at, because jam goes on thinner than buttercream.
Buttercream for the dam, if the filling is loose
| Cake size | Round | Square |
|---|---|---|
| 6 in | 69 g2.4 oz | 87 g3.1 oz |
| 7 in | 80 g2.8 oz | 102 g3.6 oz |
| 8 in | 91 g3.2 oz | 116 g4.1 oz |
| 9 in | 103 g3.6 oz | 131 g4.6 oz |
| 10 in | 114 g4.0 oz | 146 g5.1 oz |
| 12 in | 137 g4.8 oz | 175 g6.2 oz |
Two rings on a three layer cake, piped off a half inch round nozzle just inside the edge. This is on top of the filling, and it wants to be stiffer than the buttercream you coat with.
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How much filling, and why
Filling sits in the gaps between the layers, so the amount is one layer surface, times how thick you spread it, times layers minus one. Nothing about it depends on the outside of the cake.
The gaps
There is always one less gap than layers
Filling goes between the layers, so the number that drives the amount is the gaps, not the layers. Three sponges have two gaps. Four have three. This is the mistake that costs money: work a three layer cake as three fills and you make half a batch too much every time, and the cake comes out taller than the box you ordered.
The amount
One layer surface, times how thick you spread it
The filling in one gap is the area of a single layer, times the thickness, and nothing else. Surface area is what the coating tools work from, and it is the wrong basis here, because a filling never touches the sides. An 8 in round is 50 square inches, so 4 mm of jam in one gap is about 130 ml. Two gaps is a jar. If you also need the outside coated, that is the buttercream calculator, and it is a separate number.
Thickness
Jam goes on thinner than buttercream
Jam and curd are spread at 3 to 5 mm. Any more and the layers slide, because there is nothing in a fruit filling holding them together. Buttercream and ganache go on at 5 to 8 mm, and they set firm enough to be part of the structure. Whipped cream goes on thickest and weighs least, because most of it is air.
The dam
A loose filling needs a stiff buttercream ring
Jam, curd and cream all squeeze out of the sides under the weight of the sponge above, and they bleed through the coat. The fix is a dam: a ring of stiff buttercream piped just inside the edge of every layer, filled to the top and no further. Make it stiffer than your coating buttercream, more icing sugar and less liquid, and make it first. The calculator gives its weight on its own line because it is a separate thing to mix.
Filling versus batter
How full to fill the tin is a different question
If you are asking how full to fill an 8 inch tin, you mean raw batter, not filling. Fill a tin half to two thirds full, and half if you want a level layer to stack. That is worked from the space inside the tin rather than the gaps between layers, so it lives in the cake batter calculator. Size the cake first with the portion calculator if the guest count is what you actually have.
FAQ
Common questions
How much filling should I put in a cake?
About 4 mm of jam or curd per gap, or 5 to 8 mm of buttercream or ganache. On a three layer 8 inch round that is roughly 345 g of jam or 310 g of buttercream across the two gaps. Thicker than that and fruit fillings let the layers slide.
How many layers for an 8-inch cake?
Three is the standard celebration build: three sponges, two gaps, about 4 inches tall once filled. Two layers is a Victoria sandwich. Four gives a taller cake and three gaps, so it takes half as much filling again as three.
How much buttercream to fill an 8-inch cake?
About 155 g per gap at 5 mm, so roughly 310 g for a three layer cake. That is filling only. Coating the outside of the same cake takes another 350 g or so, which the buttercream calculator works out separately.
How full to fill an 8-inch cake tin?
Half to two thirds full, and half if you want a level layer that stacks without carving. That question is about raw batter rather than filling, so the cake batter calculator is the tool for it: an 8 inch round tin 2 inches deep takes about 3.5 cups of batter at half full.
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