You can use butter instead of vegetable oil at a ratio of 1 1/3 cups of melted butter for every 1 cup of vegetable oil. That is the reverse of the more common swap: because butter is only about 80 percent fat and 20 percent water and milk solids, while vegetable oil is 100 percent fat, you need more butter to deliver the same amount of fat. One cup of oil contains about 218 grams of pure fat; one cup of butter contains only about 182 grams of fat, so you need a third more butter to match it. The swap is worth doing when the recipe will taste better with butter — in a vanilla cake, a butter cookie, a brownie where the butter's flavour matters — and it is the swap to use when you have run out of oil but have butter in the fridge.

This is the direction of the swap that improves a recipe rather than merely rescuing it. A cake mix that tells you to add oil will taste better made with butter: richer, more flavourful, with a finer crumb and a golden crust from the milk solids browning. A brownie made with butter instead of oil has a more complex flavour and a chewier texture. The trade-off is that the cake will dry out faster — butter solidifies as it cools, while oil stays liquid — so a butter cake is best eaten the day it is made, while an oil cake keeps for days. For a cake that will be eaten tonight, butter wins. For a cake that needs to last the week, oil wins.

The ratio, in a table

The table below converts vegetable oil to butter for the amounts you are most likely to meet. The rule is always the same: multiply the oil by one and a third. Melt the butter first, and let it cool slightly before adding it, so it does not cook the eggs.

Vegetable oil called for Melted butter to use Notes
1 tablespoon 1 tablespoon + 1 teaspoon
2 tablespoons 2 tablespoons + 2 teaspoons
1/4 cup 1/3 cup
1/3 cup 4 tablespoons + 2 teaspoons
1/2 cup 2/3 cup
2/3 cup 7 tablespoons + 1 teaspoon
3/4 cup 1 cup
1 cup 1 1/3 cups
1 1/2 cups 2 cups
2 cups 2 2/3 cups

By weight, one cup of vegetable oil is 218 grams of fat, and 1 1/3 cups of butter is about 303 grams — of which about 242 grams is fat and the rest is water and milk solids. If you are weighing ingredients, that is the number to use. Note that you are also adding water (about 60 grams per 1 1/3 cups of butter) that the oil did not contain, so the batter will be slightly wetter. In most cakes that extra water is harmless, but if the recipe is already very wet, reduce the other liquid by a tablespoon or two.

Worked examples

Example 1: A cake mix made with butter instead of oil

A cake mix tells you to add 1/2 cup of vegetable oil. Replace it with 2/3 cup of melted butter, cooled slightly. The cake will taste richer and more homemade, with a golden crust and a finer crumb, and the vanilla flavour will come through more clearly. It will also dry out faster, so serve it the same day or wrap it tightly. This is the single most useful application of this swap: turning a box mix into something that tastes like a scratch cake, with one change.

Example 2: Brownies with a butter flavour

A brownie recipe calls for 3/4 cup of vegetable oil. Replace it with 1 cup of melted butter. The brownies will be chewier and more flavourful than the oil version, with a crackly top from the butter's milk solids and a richer chocolate taste. Let the melted butter cool for a few minutes before adding it to the eggs and sugar, or the eggs will scramble. Bake as usual, and let the brownies cool completely before cutting — butter brownies are softer when warm than oil brownies.

Example 3: A vanilla cake that needs butter's flavour

A vanilla cake recipe written for oil calls for 1 cup of vegetable oil, and you want the cake to taste of butter. Replace it with 1 1/3 cups of melted butter. The cake will have a buttery flavour that the oil version lacked, a finer crumb, and a golden colour. It will also be a little denser, because melted butter does not trap air the way creamed butter does — but in a vanilla cake, the flavour gain is worth the small texture loss. If you want the best of both, cream half the butter with the sugar and melt the rest.

What changes in the result

Three things change when you swap butter for vegetable oil. First, the flavour: butter adds a rich, creamy taste that oil does not have. In a vanilla cake, a butter cookie or a brownie, that flavour is a significant improvement. Second, the texture: butter cakes have a finer crumb and a firmer texture when cool, because butter solidifies, while oil cakes stay soft. A butter cake is best fresh; an oil cake keeps better. Third, the browning: butter's milk solids brown in the oven and add colour and a nutty note, while oil does not brown, so butter cakes look more golden.

The practical consequence is that this swap is an upgrade in flavour and a downgrade in keeping quality. Use it when the cake will be eaten the same day and the flavour matters, and do not use it when the cake needs to last for days or when the recipe relies on oil's liquid state — in a very moist cake, for example, where the oil's staying-soft quality is the point.

When not to substitute

Do not use butter instead of vegetable oil in a recipe where the oil is needed for its liquid state at room temperature — a cake that must stay soft for days, or a dressing that must stay pourable. Do not use it in frying, where the recipe calls for oil because of its high smoke point: butter burns at 150°C, while vegetable oil tolerates 220°C or more, so butter will smoke and taste bitter in a frying pan. Do not use it in a recipe where the butter would need to be creamed but the recipe was written for melted fat — the texture will change, though the flavour will improve. And do not use it if anyone eating the food is dairy-free: vegetable oil is dairy-free, butter is not, and the swap reintroduces dairy.

One more caution: melted butter is hot, and if you add it to a batter containing eggs without cooling it first, the eggs will scramble. Let the melted butter cool for five minutes, or until it is warm rather than hot, before adding it. And remember that butter contains water, so the batter will be slightly wetter than the oil version — if the recipe is already very wet, reduce the other liquid by a tablespoon per cup of butter used.

Frequently asked questions

How much butter do I use instead of 1 cup of vegetable oil?

Use 1 1/3 cups of melted butter for 1 cup of vegetable oil — about 303 grams by weight. Butter is about 80 percent fat, while vegetable oil is 100 percent fat, so you need a third more butter to deliver the same amount of fat. Melt the butter and let it cool slightly before adding it.

Can I use butter instead of oil in a cake mix?

Yes, and it is one of the best ways to improve a cake mix. Replace the oil with 1 1/3 times as much melted butter — for example, 1/2 cup of oil becomes 2/3 cup of melted butter. The cake will taste richer and more homemade, with a finer crumb and a golden crust. It will dry out faster, so serve it the same day or wrap it tightly.

Does butter make cakes dry out faster than oil?

Yes. Butter solidifies as it cools, which firms up the crumb, while oil stays liquid and keeps the crumb soft. A butter cake is at its best the day it is made; an oil cake is still moist on day three. If you are swapping butter in for oil, plan to eat the cake fresh, or wrap it well in cling film to slow the drying.

Can I use butter instead of oil for frying?

No — not for high-heat frying. Butter burns at about 150°C, while vegetable oil tolerates 220°C or more. Butter will smoke, taste bitter and burn in a hot frying pan. For frying, use oil. For baking, where the temperature is lower and the fat is protected by the batter, butter is fine. If you want butter flavour in a fried dish, fry in oil and finish with a knob of butter at the end.

Will butter change the flavour of my cake?

Yes — that is the point of the swap. Butter adds a rich, creamy flavour that oil does not have, and its milk solids brown in the oven to add a nutty note. In a vanilla cake, a butter cookie or a brownie, the flavour improvement is significant. In a strongly flavoured cake like chocolate or spice, the improvement is smaller but still noticeable.

Can I use salted butter instead of oil?

Yes, but reduce the salt in the recipe. Salted butter contains about 1 to 2 percent salt, so 1 1/3 cups of salted butter adds roughly a teaspoon of salt to the recipe. If the recipe already contains salt, reduce it by that amount, or the cake will taste salty. Unsalted butter is the better choice for baking, because you control the salt separately.

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