Counting slices before you choose a size
Bakeries size round cakes by diameter, and the number of slices depends on how thin you cut. A two-layer 6-inch round gives roughly 8 to 12 servings, an 8-inch about 14 to 20, and a 10-inch somewhere near 25 to 30 if you cut the narrow party wedges most decorators assume. Sheet cakes stretch further: a quarter sheet usually feeds 20 to 25 people, and a half sheet 40 to 50.
When the guest list is mostly small children, you can size down; for a crowd of adults who skipped dessert elsewhere, size up one step. A cake that is a little too big costs less than a cake that runs out before the last guest gets a piece.
Grab-and-go case cakes versus a placed order
Many bakeries keep a few decorated cakes in the refrigerated case, usually 6- or 8-inch rounds in chocolate, vanilla and one or two house favorites. Ask, and staff can often pipe a short message on one while you wait. Expect roughly $25 to $50 for a small case cake at an independent bakery, with supermarket bakeries tending to run lower.
A placed order opens up flavor pairings, fillings, colors and a theme. Most shops want two to seven days' notice for a standard decorated birthday cake, more for tiered or sculpted work, plus a deposit when you order. An 8-inch custom birthday cake commonly lands between $50 and $120, depending on decoration and where you live.
Picking a frosting that survives the party
- American buttercream (butter beaten with powdered sugar) is sweet, crusts slightly and holds piping well, which makes it the default for writing and borders.
- Swiss or Italian meringue buttercream is silkier and less sugary but softens faster in heat.
- Whipped cream is light and standard at many Latin American and Asian bakeries; it has to stay cold and does poorly at outdoor parties.
- Cream cheese frosting belongs on carrot, red velvet and spice cakes and also needs the fridge.
- Fondant gives a smooth, matte surface for printed or sculpted designs, though plenty of guests peel it off.
For a backyard party in July, ask the baker which of their frostings holds best out of the cooler, and plan to cut the cake early rather than leaving it on the table for hours.
Small details people forget until the day
Spell out the name exactly as it should appear, including nicknames and accents, and check it again at pickup. Candles, number toppers and a cake knife are not always included. If anyone at the party has a nut allergy, ask whether the kitchen handles nuts on shared equipment, not just whether this particular cake contains them. Carry the box flat on the floor of the car rather than on a seat, which tilts, and keep the air conditioning running on warm days.
