How Many People Can a Costco 1/2 Sheet Cake Feed? Portion Size & Serving Guide

It’s wild how any mention of a Costco sheet cake makes people perk up. These cakes have reached almost cult status, showing up at everything—from baby showers to last-minute office parties—because they’re cheap, huge, and strangely delicious for mass-produced dessert. If you’re the one in charge of feeding a crowd, you probably want to make sure you buy enough cake without ending up with enough leftovers to build another cake altogether. But what does "1/2 sheet" even mean in Costco-speak? How many guests can you treat with one of these monster cakes, and what else should you know before you wrangle this slab into your shopping cart? Let’s break it down.

What Exactly Is a Costco 1/2 Sheet Cake? Size, Slices, and Surprising Specs

First, this isn’t just any old cake you’d bake at home in a pan. When Costco says "1/2 sheet cake," they really mean business. The standard Costco half sheet cake measures approximately 12 inches by 16 inches. That surface area alone gives you about 192 square inches of sugary joy. These cakes are more like dessert districts than slices—they’re big enough to make birthday candles look tiny and can flatten the back seat of a small car.

What sets the Costco half sheet cake apart isn’t just quantity. Each cake is about three inches tall, stuffed with real cake layers and thick frosting. They come in classic flavors—like vanilla cake with vanilla cheesecake mousse filling or chocolate cake with chocolate mousse, both covered in a dense, sweet icing that’s become somewhat legendary (and let’s be real, a little divisive; people either love it or leave it on the plate).

Here's a quick size comparison to other cakes:

That half sheet from Costco is huge: it’s twice as large as a typical grocery store quarter sheet cake. No wonder it’s a staple for big families, clubs, and, let’s be real, anyone who just loves cake leftovers.

Each cake is pre-scored for convenience. If you actually follow their cutting lines (most people don’t), you end up with about 48 neat rectangles, each about two by two inches. Perfect slices for a casual gathering, but you’re really in control. Want bigger pieces? You’ll get fewer servings. Tea party-style slivers for a more dainty affair? You’ll stretch it out further. The beauty is in the flexibility.

How Many People Does a Costco 1/2 Sheet Cake Feed? Real Party Math

This is the big question—the one party hosts inevitably end up Googling from the bakery aisle. Officially, Costco says their 1/2 sheet cake serves 48 people. That’s with standard two-inch by two-inch slices, which are pretty generous for something this sweet and rich. But real life doesn't always stick to the script. So, how does this break down for different crowds?

• Kids’ Birthday Parties: Kids rarely finish a whole piece, especially with sugar highs and distractions. Expect to serve up to 60 small slices if you cut them about 2” x 1.5”—trust me, nobody will complain.
• Office Parties or School Events: Adults tend to take a normal chunk, but some folks will go back for seconds (c’mon, it’s Costco cake). Forty-eight servings is usually spot on, but I’ve seen hosts stretch it closer to 54-60 if you cut more carefully.
• Big Family Gatherings or Potlucks: You know how it is—people want to try a little of everything, cake included. Cutting the pieces thinner gets you 60+ servings, easy.

Check out this serving guide for the breakdown based on how you plan to cut it:

If you want a big wow factor for dessert but don’t want to spend all night cutting and serving, the 1/2 sheet is your friend. Just remember: the size of the slice decides everything. Also, leftover Costco cake keeps shockingly well—you can even freeze it for months.

Worried about leftovers? Here’s a hack: Ask your Costco bakery to score the cake ahead of time for you. They’ll do it if you request it when you order. Makes serving a whole lot quicker and the pieces look way more uniform (perfect for Instagram pics, if you’re into that sort of thing).

Tips for Ordering, Storing, and Serving Costco’s 1/2 Sheet Cake Like a Pro

Getting the most from your giant cake isn’t just about portion math. Here are a few insider moves people often overlook:

• Advance Ordering: While some warehouses have them ready to grab-and-go, custom designs or writing require a 2-3 day notice. You can call, use the paper form at the bakery counter, or order online (in locations where it’s available). Avoid the heartbreak—order ahead during peak seasons like graduations or holidays.
• Flavor Lockdown: For years, choices were vanilla or chocolate. Check periodically—some warehouses have brought back fun flavors for special events (like marble or carrot). Never hurts to ask!
• Storage Smarts: Keep it in the fridge until about two hours before serving. It helps the icing firm up for clean cuts, but nobody wants cold, dense cake straight from the chill. Just let it sit at room temp, still in the box, and it’ll be perfect by party time. Got leftovers? Slice, wrap tightly in plastic, and pop pieces in the freezer. When cravings strike, just thaw a piece—it’s fresher than you’d expect.
• Allergy/Ingredient Check: Costco cakes contain eggs, wheat, dairy, and soy—and lots of sugar and artificial flavors. For gluten-free or vegan guests, you’ll need alternate options (sadly, Costco doesn’t do specialty diet sheet cakes as of August 2025).
• Decorating Secrets: Costco’s basic designs cover major events—birthdays, graduations, retirements, even blank white canvases for DIY fun at home. Want to add fruit, sprinkles, or custom toppers? Their plain white cake is your blank slate. Plus, you can choose from over two dozen design options or bring in your own themed decorations to upgrade your party style.
• Serving Like a Pro: Use a straight-edge knife (run it under hot water, wipe, repeat for each cut), and slice with confidence if you want those photo-ready squares. If you’re worried about crumbs in the frosting, a thin offset spatula can help keep things clean. Want smaller servings for kids? Cut the standard 2" x 2" slice diagonally for two triangles. It’s cute and feels like a bigger portion.

There’s an odd joy in being the person who shows up with a Costco 1/2 sheet cake. People gather around, guessing flavors, picking at corner roses, and yes, arguing about the best frosting-to-cake ratio (corner is always best—don’t fight me on this).

Looking to stretch your budget? These cakes cost under $30 (as of summer 2025), which is absolutely unbeatable. If you were to try and bake this much cake at home, factoring in the time, ingredients, and stress, you’d spend more than double and end up washing dishes for hours.

Long story short: if you’re feeding a crowd, nothing beats the sheer value, convenience, and nostalgia of a Costco 1/2 sheet cake. Whether you’re planning for exactly 48 guests or want to err on the side of extra, you can easily stretch one of these cakes to serve almost anyone who comes hungry—and have a few slices left to sneak for breakfast the next day (no judgment). Next time you hear, “Who’s bringing dessert?”—you know what to do.