How this instrument works
How many slices a cake yields comes down to two things: its total top-surface area, and how much area you're allotting to each serving. A round cake's area follows the standard circle formula (pi times the radius squared); a rectangular sheet cake's area is simply length times width. Once you know the total area, dividing by your serving size and rounding down to a whole slice tells you exactly how many people the cake will feed.
The most common party-style serving size is 2 inches by 2 inches — 4 square inches per slice — a size that works for a casual gathering where cake is one of several desserts on the table. Wedding-style servings tend to be smaller (closer to 1 x 2 inches), and a dessert-only event might use larger slices. This calculator defaults to the 4-square-inch party standard but lets you set any serving size you're planning around.
- Choose round or rectangular as your cake's shape.
- Enter the diameter for a round cake, or the length and width for a rectangular one.
- Set your serving size in square inches, or keep the 4 sq in party-style default.
- Read off the total cake area and the number of servings it yields.
A 26 x 18 inch full sheet cake
A standard full sheet cake measuring 26 inches by 18 inches has an area of 26 x 18 = 468 square inches. At the standard 2 in x 2 in (4 sq in) party-style serving size, that's floor(468 / 4) = 117 servings — a figure large enough to comfortably cover a sizeable wedding or office party from a single sheet.
For comparison, a 12-inch round cake — a common single-tier size — has an area of pi x 6^2 ~ 113.1 square inches, yielding floor(113.1 / 4) = 28 servings at the same 4 sq in slice size. The rectangular sheet's larger footprint is why it's the standard choice for feeding a much bigger group from one cake.
Questions
Why does a 26x18 sheet cake give exactly 117 servings at 4 sq in?
The cake's total area is 26 x 18 = 468 square inches, and dividing that by a 4-square-inch serving size gives exactly 117.0 with nothing left over — a clean round number because 468 happens to divide evenly by 4. In cases where the division doesn't come out even, this calculator rounds down to a whole serving, since a fractional slice isn't something you can actually serve as one portion.
What serving size should I use for a wedding versus a casual party?
Wedding cake servings are traditionally smaller than casual party servings — often closer to 1 inch by 2 inches (2 square inches) rather than the 2x2 inch (4 square inch) party standard, since wedding cake is typically one of several desserts and guests expect a smaller taste. If you're planning a formal event, try running the calculator at 2 square inches per serving instead of the 4 square inch default to see how many more slices the same cake yields.
Does this account for cake height or number of tiers?
No — this calculator works purely off the top-surface area of a single layer or tier, since serving size is conventionally measured as a footprint (width x depth of the slice) rather than a volume. For a multi-tier cake, run each tier through the calculator separately using its own diameter or dimensions, then add the resulting serving counts together to get the cake's total yield.
Should I round the serving count down or up when planning?
This calculator already rounds down, which is the safer default for planning purposes — it guarantees every serving is a full one rather than assuming you can stretch the cake with a partial slice that doesn't really work as a portion. If you're planning tightly for a fixed guest count, it's still worth leaving a small buffer, since not every slice cuts perfectly evenly in practice.