A Slab Cake is a large, flat, single-layer, rectangular cake. It is not quite the same as a “Sheet Cake”, though both can be used to serve large numbers of people.
The usual purpose of a Slab Cake is to provide cake for large birthday parties.
The size varies widely. Slab Cake is not a legal term, and bakeries are free to define a slab as whatever they want.
At bakeries, the most common “standard size” for a full slab cake is 16 x 24 inches (40 x 60 cm), and about 3 inches (7 1/2 cm) tall.
Generally, bakeries sell them by the 1/2 slab (16 x 12 inches / 20 x 30 cm.)
To make a very long slab cake for a huge crowd, you can put two full slabs (16 x 24 inches / 40 x 60 cm) together on a plywood board, and decorate them to look like one cake. Practical reminder though: the larger the slab cake, the smaller your chances are of finding a fridge to store it in.
Slab Cake is usually sold already decorated, but from proper bakeries (as opposed to in-store ones) you can get undecorated ones to decorate at home.
When sold decorated, they are often covered with a protective plastic “roof” cover. Some people save these covers and use them in the spring as miniature greenhouses for their seedlings.
You can order a slab cake already cut, ready to serve. Some caterers working for you will strongly prefer for them to come already cut, and might even reduce their “plating charges” if it is. Some bakeries will cut the cake, then ice and decorate it so it still looks just as good, but somehow demark with the decorations where the server should guide the serving knife.
The quality of store-bakery ones is considered generally to be relatively low, but most people still buy them anyway, as they are a quick, cheap and cheerful way to feed the masses and the convenience of a store-bakery when rushing about preparing a party is often hard to resist.
Always check the number of servings with the person you are buying the cake from. The number of people that a particular size of slab cake is estimated to serve varies wildly. You’ll see some bakeries saying 80 servings from a full slab, some saying 200 servings from a full slab. This is because some slab cakes are shorter or taller than the “standard” 3 inches (7 1/2 cm.) Some bakeries may also make a shorter “Sheet Cake” 2 inches (5 cm) tall and call it a Slab Cake. A shorter cake will serve fewer people, putting a full slab in the 80 servings range. Some bakeries may make them taller. For instance, a bakery called “Major the Gourmet” in Vancouver, Canada, says its slab cakes are an average of 5 inches (12 1/2 cm) tall. Taller ones will serve more people, putting a full slab in the 200 servings range.
Only a direct inquiry will sort out the actual size of the cake and the sizes of the pieces of cake the bakery is basing its serving estimates on.
SizeNumber of slices
2 x 2 inch (5 x 5 cm) Number of people12 x 18 inches (30 x 45 cm)5420 to 40 people16 x 24 inches (40 x 60 cm)
(full slab)9696 to 150 people16 x 48 inches (40 x 120 cm)
(two slabs joined side-by-side)192200 to 300 people
Definitions of a homemade Slab Cake range from 8 x 12 inches (20 x 30 cm) to 10 1/2 x 12 1/2 inches (27 x 32 cm.)
Lamingtons in Australia are baked at home in small, home-size slab pans.