Chocolate Sheet Cake

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Chocolate sheet cake is a moist and tender homemade cake with rich chocolate flavor. The velvety whipped chocolate buttercream frosting makes it perfect for chocolate lovers! This recipe can be made in a 9x13 or 13x18 pan.

Chocolate 13x18 sheet cake slice served on a plate.

After many reader requests, I've made sheet cake recipes out of my much-loved cupcake recipes, like vanilla sheet cake and lemon sheet cake. Today it's chocolate's turn - we're turning my chocolate cupcakes recipe into a cake!

This cake is made with simple baking ingredients and can be prepared in two different pan sizes. Instructions for each are included in the recipe card.

Serve chocolate sheet cake at your next picnic, celebration, or birthday party. It's perfect any time of year!

Ingredients and substitutions

Since baking is an exact science, I do not recommend substituting any ingredients in this recipe. If you do not have the listed ingredients on hand, I recommend searching for a recipe that includes the ingredients available to you.

All-purpose flour - I use all-purpose flour in my chocolate cakes because the wet ingredients are heavier and thicker (specifically the oil and buttermilk), so the batter benefits from the added structure of AP flour.
Cocoa powder - You'll want to use natural cocoa powder for this recipe, not Dutch-processed cocoa powder. Natural cocoa powder is more acidic than Dutch cocoa powder. When paired with the leavening agents in this recipe it gives your cake the proper rise. What happens if you use Dutch cocoa anyway? Your cake will rise less in the oven and have a darker color.
Leavening - You'll need a combination of both baking soda and baking powder to get the proper lift.
Salt - Enhances the flavor of your cake without making it "salty".
Granulated sugar - Sugar adds sweetness, moisture, and acts as a preservative in your cake. I have not tested this recipe with sugar substitutes. If you don't want to use granulated sugar in your cake, I highly recommend searching for a chocolate cake recipe made with the sugar substitute you'd like to use.
Eggs - Eggs add structure and moisture to your cake. Room temperature eggs are best for baking because they blend seamlessly into the batter without lumps or streaks.
Buttermilk - Adds moisture, a hint of tang, and the proper acidity to your cake batter. If you don't have buttermilk on hand, a buttermilk substitute can be made. In a liquid measuring cup, add 1 tablespoon of white vinegar. Fill to the 1-cup line with whole milk and allow to set for 5 minutes. This makes a proper buttermilk substitute with the right amount of acidity for the recipe.
Warm water - Added to the batter to thin it slightly so your cake rises properly. Without water, the batter is too dense and heavy, making it likely to sink in the center.
Vegetable oil - Adds moisture to your cake. I prefer to use oil in chocolate cake for a few reasons. Oil gives cake a velvety, extra-moist texture that can't compare to cakes made with butter. While butter adds a better overall flavor to recipes like vanilla cake, it can't compete with the strong flavor of cocoa powder, making it an unnecessary addition.
Vanilla extract - Enhances the flavor of your cake.

Cake tips and tricks

Mixing chocolate cake batter in a glass bowl.

Mise en place - This is a French culinary term that refers to the gathering of ingredients and setup required before cooking. Read the entire recipe from beginning to end, then prepare all of the ingredients before beginning. This ensures you don't skip a step or ingredient in the cooking process.

Bring eggs to room temperature - Room temperature eggs blend seamlessly into the batter without leaving and streaks or lumps. To bring eggs to room temperature, place on the countertop 30 minutes before beginning. You can also place whole eggs into a bowl and cover with warm tap water. Using this method, your eggs will come to room temperature in about ten minutes.

Don't overmix the batter - Mix your dry ingredients just enough to incorporate them into the batter. Overmixing can overwork the gluten, causing your cake to turn out tough.

Don't omit or reduce any of the moisture-adding ingredients - Oil, buttermilk, eggs, and granulated sugar all do their part in ensuring your cake turns out moist and tender. Reducing, omitting, or substituting these ingredients can cause your cake to turn out dry.

Frosting tips and tricks

Frosting chocolate sheet cakes in multiple sizes.

Use a hand mixer or stand mixer - This frosting must be whipped with a whisk attachment for several minutes, so I recommend using a mixer instead of trying to mix it by hand.

Don't skip the salt - The salt listed in this recipe helps balance with the sweetness of the frosting and enhances the flavor.

Use heavy cream - To ensure your frosting whips up nice and fluffy, use heavy cream. If you need to use milk, use less (start with a few tablespoons at a time) because milk won't whip up like heavy cream does. Adding extra milk will cause your frosting to turn out thin.

Frosting quantity - This recipe makes enough frosting to add a thick layer across the top of your sheet cake in either size chosen. If you'd prefer less frosting, make a half batch instead.

Do not frost a warm cake - Buttercream frosting melts around 90 degrees Fahrenheit. Adding frosting to a hot cake will cause it to melt. Wait until your cake is completely cooled.

Storage

Chocolate cake in a 9x13 metal pan with one slice served on a plate.

Homemade cakes are best served the same day they are baked for best flavor and texture. However, there are solutions if you need to make your cake a few days (or weeks) ahead of time.

Room temperature - Frosted cake can be stored in a tightly sealed container (or wrapped well with foil) at room temperature for 2-3 days, but will begin to dry out over time.

Frozen - Cake and frosting freezes and thaws beautifully, maintaining its original texture and moisture just like the day it was baked. Unfrosted or frosted cake can be frozen for up to two months. To store a frosted cake, first freeze for an hour, unwrapped, until firm. Gently wrap in plastic and store in a tightly sealed container for up to 2 months. Thaw your cake in the refrigerator overnight, then bring to room temperature 30-60 minutes before serving.

Refrigerated - I do not recommend this option unless you live in a hot or tropical climate. Refrigerators are a low humidity environment and dry out cake faster than storing at room temperature or freezing. Unfrosted or frosted cake can be refrigerated for 3 to 4 days if needed. Wrap unfrosted cake in plastic and store in a sealed container. Bring to room temperature 30-60 minutes before serving.

Hot climates - Buttercream frosting should not sit out in the sun or a hot room for extended periods of time because it melts at about 90 degrees Fahrenheit. If it's summertime or you live in a tropical climate, you may need to store your buttercream frosted cake in the refrigerator until 30 minutes before serving to prevent melting.

Frequently asked questions

What size pan do I need?

This recipe works in three different sizes: a 9x13 baking pan (with 2 inch tall sides), two 9-inch round cake pans, or a 13x18 half sheet pan (with 1 inch sides).

Both the 9x13 and 13x18 sheet cakes can remain in the pan after baking. Simply frost, slice, and serve! To make this as a layer cake, follow my recipe for chocolate layer cake.

What are your favorite cake pans?

Here are the cake pans I recommend for making vanilla sheet cake:

- Nordic Ware Classic Metal 9x13 Covered Cake Pan
- Natural Aluminum Nordic Ware Commercial Baker's Half Sheet (2 Pack)
- Nordic Ware 9" Round Natural Aluminum Cake Pans (2 Pack)

How do I make buttercream frosting less sweet?

Buttercream frosting is a traditional, very sweet frosting that is often found in grocery store bakeries and on birthday cakes. It is popular because it's easy to prepare with just two main ingredients - butter and confectioner's sugar. Since buttercream includes so few ingredients, it is not easy to alter to make less sweet. Adding less sugar makes the frosting too soft to pipe and also tastes like sweetened butter.
Instead, I'd suggest making a less sweet frosting recipe. All of these frostings are less sweet that buttercream: ermine frosting, chocolate ermine frosting, homemade whipped cream, chocolate Italian meringue buttercream, and chocolate Swiss meringue buttercream.

How should I store a frosted cake before serving?

Baked goods can be frosted with buttercream the day before an event and left at room temperature in a sealed container. Keep in mind that butter (and in turn, buttercream) melts around 90 to 95 degrees Fahrenheit.
If your location is nearing this temperature, I'd recommend refrigerating your baked goods until an hour before you're ready to serve them. Refrigerating your frosted baked goods for a short amount of time will not hurt them. However, you will want to give them some time to come to room temperature before serving.
Here's a fantastic article about how frosting holds up to heat: The Best Cake Frosting For Hot Weather

Can I pipe decorations with this frosting?

Yes, this frosting pipes beautifully and can be used for rosettes, borders, and topping cupcakes.

How do I know when my cake is done?

Check your cake for doneness by jiggling the pan - if it moves, it's not done yet. If your cake isn't jiggly in the center, gently press onto the top with a finger. If an indent is left, it needs more time. If it pops right back, your cake is done.
The toothpick method is another popular way to check for doneness. Insert a toothpick into the center of your cake. If the toothpick comes back dry or with a few dry crumbs your cake is done. If the toothpick has wet batter or very moist, clingy crumbs, your cake needs more time.

How many people does this recipe serve?

This recipe can be sliced to serve as many as 30-40 people with small slices (think wedding cake slices). Larger squares will yield about 16 slices.

Troubleshooting

Why did my cake turn out dry?

One of the most common complaints I see in baking is that the recipe is followed "to a T" and the cake/cookies still turn out dry. Dry baked goods can happen for several reasons:
- Ingredients were substituted/omitted/reduced - The fats and sugar (oil, buttermilk, eggs, and granulated sugar) help keep your cake moist. Using lower fat substitutions, reducing the sugar, or omitting an ingredient entirely will cause your cake to turn out dry.
- Too much flour was added to the recipe - Either use a kitchen scale to weigh your flour accurately (which is how I measure flour and highly recommend to others), or spoon the flour into your measuring cup and level off with a knife. Scooping with the measuring cup directly from a bin of flour compacts it into the cup, adding up to 25% extra flour to the recipe.
- Cake was overbaked - Baking a cake for too long will dry it out in the oven. Ovens are inconsistent and can run hotter or colder than the next oven. The time that worked for me may not work for you, so I recommend using other cues to tell when your cake is done.

How do I add moisture to a dry cake?

This is a baker's secret that's optional but effective! Brush simple syrup over your cake before frosting. A layer of simple syrup helps keep the cake moist for longer. Simple syrup is a 1:1 ratio of water and granulated sugar, brought to a boil on the stove top until dissolved, then cooled to room temperature. I'd suggest about ¼ cup or more for this size cake.

Why did my cake turn out dense?

Cake can turn out dense from expired leavening, overmixing the wet and dry ingredients (this overworks the gluten) or adding extra wet ingredients (like adding sour cream or applesauce to make cake "extra moist"). If the balance of wet and dry ingredients is off, this can cause a change in texture, preventing your cake from rising properly in the oven.

Why did my cake sink in the middle?

Sinking can happen for many reasons. Overmixing the batter (which adds extra air that's released during baking), underbaking, using expired leavening, using the wrong leavening, or accidentally doubling the leavening can all cause your cake to sink in the middle.

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