You can use vegetable oil instead of butter at a ratio of 3/4 cup of vegetable oil for every 1 cup of butter. The rule is the same as for olive oil, and for the same reason: butter is about 80 percent fat and 20 percent water and milk solids, while vegetable oil is 100 percent fat, so you need less oil to deliver the same amount of fat. The difference between this swap and the olive oil swap is flavour — vegetable oil is neutral, so it disappears into the recipe, while olive oil announces itself. That neutrality makes vegetable oil the safest, most invisible butter substitute in baking, and the one to reach for when you want the recipe to taste exactly as written, just without the butter.

Vegetable oil is the workhorse fat of the boxed-cake-mix world for a reason. Almost every cake mix on the shelf tells you to add oil, not butter, because oil makes a cake that is moist on day one and still moist on day three, that mixes in seconds with no creaming, and that never goes wrong because you forgot to soften the butter. A scratch cake made with vegetable oil will not have the rich flavour of a butter cake, but it will have a reliably tender crumb and a long shelf life, and for a weeknight birthday cake or a school bake sale, that reliability is worth more than the flavour difference.

The ratio, in a table

The table below converts butter to vegetable oil for the amounts you are most likely to meet. The rule is always the same: multiply the butter by three quarters. For small amounts, the tablespoon figures are the useful ones.

Butter called for Vegetable oil to use Notes
1 tablespoon 2 1/4 teaspoons Round to 2 teaspoons
2 tablespoons 1 1/2 tablespoons
1/4 cup 3 tablespoons 45 ml
1/3 cup 1/4 cup 60 ml
1/2 cup 6 tablespoons 90 ml
2/3 cup 1/2 cup 120 ml
3/4 cup 9 tablespoons 135 ml
1 cup 3/4 cup 180 ml
1 1/2 cups 1 1/8 cups 270 ml
2 cups 1 1/2 cups 360 ml

By weight, one cup of butter is 227 grams and three quarters of a cup of vegetable oil is about 164 grams (vegetable oil weighs 218 grams per cup). If you are weighing ingredients, that is the number to use. You are also removing the water that butter contains — about 34 grams per cup — and the milk solids that brown and add flavour. In most cakes and muffins that loss does not matter, but it is worth remembering if the recipe is one where butter's browning is part of the flavour, such as a brown-butter cake.

Worked examples

Example 1: A weeknight chocolate cake from a box-style recipe

A chocolate cake recipe calls for 1/2 cup of butter, and you have no butter in the fridge. Replace it with 6 tablespoons of vegetable oil, whisked with the sugar and eggs. The cake will mix in two minutes — no waiting for butter to soften, no creaming, no fuss — and it will come out moist with a fine, even crumb. It will not taste as rich as the butter version, but in a chocolate cake the cocoa dominates the flavour anyway, so the difference is small. This is the swap's best use: a cake where the flavour comes from something else, and the fat's job is purely structural.

Example 2: Banana bread that stays moist for a week

A banana bread recipe calls for 1/3 cup of butter. Replace it with 1/4 cup of vegetable oil (60 ml). Banana bread is already moist from the bananas, but the oil keeps it soft for days longer than butter would, because oil does not solidify as it cools. A butter banana bread firms up in the fridge; an oil banana bread stays soft. Mash the bananas, stir in the oil, sugar and eggs, fold in the flour, and bake as usual. If the recipe calls for creaming the butter and sugar, skip that step — just whisk the oil and sugar together until combined.

Example 3: Muffins for a school bake sale

A muffin recipe makes 12 muffins and calls for 1/4 cup of butter. You are tripling it for a bake sale, so you need 3/4 cup of butter — or, with the swap, 9 tablespoons of vegetable oil (135 ml). Measuring 9 tablespoons of oil is faster and cleaner than measuring 3/4 cup of butter, and the muffins will be uniformly moist across all three batches, which matters when you are baking 36 muffins and cannot afford a dry batch. The neutral oil also means the muffins taste of their flavourings — blueberry, chocolate chip, lemon — rather than of butter, which is what you want in a muffin.

What changes in the result

Three things change when you swap vegetable oil for butter. First, the flavour: you lose butter's rich, creamy taste. In a vanilla cake or a butter cookie, that loss is noticeable; in a chocolate cake, a spice cake or a banana bread, it is barely noticeable. Second, the texture: oil-based cakes are moister and stay soft longer, but they are denser, because oil cannot trap air the way creamed butter does. A cake made with oil will never be as light as a cake made with properly creamed butter, and it will have a finer, more even crumb rather than a fluffy one. Third, the keeping quality: oil cakes stale more slowly, which is a genuine advantage for anything that will be eaten over several days.

The practical consequence is that the swap is best in recipes where the fat is melted or liquid anyway — muffins, quick breads, traybakes, chocolate cakes — and worst in recipes where the fat's solid state matters. Creaming is the clearest example: beating butter with sugar traps air that lifts the cake, and oil cannot do this. Pastry is the other example: butter's solid fat creates flakiness, while oil makes a crumbly pastry. And frosting is the third: buttercream needs butter's solid structure to whip and hold its shape, and oil will never do that.

When not to substitute

Do not use vegetable oil instead of butter in recipes that rely on creaming butter with sugar (sponge cakes, most layer cakes, many cookies), in laminated pastry (croissants, puff pastry, Danish), or in shortbread, where butter is the dominant flavour and the entire structure. Do not use it in buttercream or frosting. Do not use it where the recipe calls for browning the butter — brown butter's nutty flavour has no equivalent in neutral oil. And do not use it in a recipe where the butter is the point: a butter cookie, a kouign-amann, a butter cake. In those recipes, the butter is not an ingredient you can swap; it is the recipe.

One more caution: vegetable oil is usually a blend of soybean, canola or sunflower oil, and its exact composition varies by brand and country. That does not change the ratio — all neutral oils weigh about 218 grams per cup and behave the same way in baking — but if anyone eating the cake has a soy allergy, check the label. Canola oil is a good alternative if soy is a concern, and it swaps at exactly the same ratio.

Frequently asked questions

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

Use 3/4 cup of vegetable oil for 1 cup of butter — 180 ml, or about 164 grams by weight. Butter is about 80 percent fat and 20 percent water and milk solids, while vegetable oil is 100 percent fat, so you need less oil to get the same amount of fat.

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

Yes — in fact, most cake mixes already tell you to use oil rather than butter. If a mix says to use 1/2 cup of oil, use 1/2 cup of oil; do not apply the butter ratio, because the recipe was already written for oil. If a scratch recipe calls for butter and you want to use oil, apply the 3/4 rule: 1 cup of butter becomes 3/4 cup of oil.

Does vegetable oil make cakes greasy?

It can, if you use too much. The most common mistake is swapping cup for cup — 1 cup of oil for 1 cup of butter — which adds a third too much fat and makes the cake greasy and heavy. Use the 3/4 ratio and the cake will be moist, not greasy. If your oil cake still tastes greasy, check whether you also added the butter's water: some bakers add a tablespoon of water or milk per cup of oil to replace the water butter would have contributed, but that is usually unnecessary.

Can I use vegetable oil instead of butter in cookies?

In soft, chewy cookies, yes — the cookies will be flatter, chewier and stay soft longer. In cookies that rely on creamed butter for lift and structure, no — the cookies will spread too much and taste oily. For a chocolate chip cookie, the swap works well; for shortbread or a delicate sugar cookie, it does not.

Is vegetable oil healthier than butter?

Vegetable oil is lower in saturated fat than butter, but it is still a calorie-dense fat — about 120 calories per tablespoon, compared with about 100 for butter. Whether it is "healthier" depends on the oil: canola and sunflower oils are high in monounsaturated fats, while some blended vegetable oils are higher in omega-6 fats. The swap is a reasonable choice if you are avoiding dairy or saturated fat, but it is not a low-calorie choice.

What is the difference between vegetable oil and canola oil in baking?

Very little. Both are neutral-flavoured oils that swap for butter at the same 3/4 ratio and weigh about the same per cup. Canola oil has a slightly better fat profile (more monounsaturated fat) and a higher smoke point, which makes it better for frying. For baking, they are interchangeable — use whichever you have.

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