How to Substitute Butter for Vegetable Oil When Baking a Cake

Baking has a reputation as the chemistry class of home cooking, a place where precision is mandatory and any slip-ups will result in a failed experiment. There’s an element of truth to that idea, but also a lot of exaggeration. Bakers often improvise on the fly when an ingredient is unavailable or when they’re trying to upgrade a recipe. Swapping out oil for butter, for example, usually improves a cake.

In any cake, the fat serves a few distinct purposes. It gives the cake tenderness, adds richness, and helps the cake feel moist and luscious in your mouth. Some fats, including olive oil, butter, and even lard or bacon fat, add a distinctive flavor in some recipes.

Vegetable oil is a relatively neutral, clean-flavored fat, so when it’s called for in a recipe, it’s there purely to soften, enrich and moisten the cake’s crumb. That means it’s also easy to substitute if you don’t have oil on hand, or if you’re looking to give your cake a little something extra. Arguably, the best and most obvious replacement for vegetable oil is butter.

In a cake that calls for vegetable oil, swapping out the oil for butter does a couple of things. First, butter makes a cake slightly moister, because it contains some water along with its fat. Secondly, and most notably, it brings extra flavor and richness to the crumb. On the downside, adding butter makes the cake unsuitable for anyone avoiding dairy because of allergies, kashruth or other dietary restrictions.

One obvious issue with substituting butter for oil is that oil is a liquid fat at room temperature, while butter is solid. To use butter as a canola oil substitute or vegetable oil substitute, melt it first in the microwave and then let it cool to room temperature while you’re assembling your other ingredients. When it’s barely warm to the touch, it’s ready to use.

When you’re making up a cake mix, substituting butter for the oil is a straightforward process. Cut and melt your butter, ideally in a microwave-safe measuring cup, so you can be sure you’ve actually cut the correct amount. The lines printed on the butter’s wrapper don’t always line up properly with the stick inside.

Once the butter has cooled, add it to your mixing bowl when you would otherwise add the oil. If you’re using butter specifically to amp up the flavor of your box mix and make it taste more like homemade, you can opt for a few other tweaks as well. A splash of good-quality vanilla extract elevates any cake, fresh spices will help a spice cake, a spoonful of cocoa helps a chocolate cake, and so on. Once the cake is mixed, bake it as directed on the box.

Relatively few scratch cakes call for oil. Some are chef-ly creations meant to showcase the fruity flavors of good olive oil, but most of the rest are chiffon cakes. These are light and airy, like an angel food cake, but they have a richer flavor thanks to the addition of eggs and oil. They have to be handled carefully, because fat has the nasty habit of deflating your egg whites and taking away some of the cake’s fluffiness.

The basic technique with a chiffon cake is to beat the oil – or in this case, melted butter – into the cake-y part of the batter, and then to carefully lighten the batter by folding in the beaten egg whites. It’s usually easiest to incorporate the first 1/4 or so of the egg whites thoroughly to thin the batter; then fold the remainder carefully to preserve the foaminess of the egg whites as much as possible.

You can use melted butter as a direct 1:1 substitute for oil, but only up to a point. Because butter contains up to 15 percent water, if you’re making more than a single recipe, that moisture makes a difference. For double batches of a scratch cake or two boxes of mix, you may find it best to reduce your liquids by a couple of tablespoons for every cup of butter you use.

The other thing to know is that it’s only a one-way trip. You can’t substitute oil for butter in most cake recipes because butter is a solid and serves a structural purpose. When you cream the butter and sugar together, you’re creating millions of tiny air pockets in the butter. As the cake bakes, those air pockets trap gas created by the recipe’s baking powder or soda. Without butter, the cake will be relatively dense and have a disappointing, leathery texture.