Use 3/4 cup of oil for every 1 cup of butter. This 3:4 ratio by volume accounts for butter’s water content — butter is about 80% fat and 16% water, while oil is 100% fat. Using the same volume of oil would add significantly more fat than the recipe intends.
For recipes that already call for melted butter (brownies, many quick breads), a 1:1 swap also works and gives a slightly moister result.
Use the butter converter to convert any butter amount to oil quickly.
Butter to oil conversion chart
| Butter | Oil (3:4 rule) |
|---|---|
| 1 teaspoon | 3/4 teaspoon |
| 1 tablespoon | 2 1/4 teaspoons |
| 2 tablespoons | 1 1/2 tablespoons |
| 1/4 cup (1/2 stick) | 3 tablespoons |
| 1/3 cup | 1/4 cup |
| 1/2 cup (1 stick) | 1/4 cup + 2 tablespoons |
| 2/3 cup | 1/2 cup |
| 3/4 cup (1.5 sticks) | 1/2 cup + 1 tablespoon |
| 1 cup (2 sticks) | 3/4 cup |
| 2 cups (4 sticks) | 1 1/2 cups |
Oil to butter (reverse conversion)
To go the other way — oil in a recipe, want to use butter — multiply by 4/3:
| Oil | Butter needed |
|---|---|
| 1/4 cup | 1/3 cup |
| 1/3 cup | 7 tablespoons |
| 1/2 cup | 2/3 cup |
| 3/4 cup | 1 cup (2 sticks) |
| 1 cup | 1 1/3 cups |
Why butter is about 80% fat (not 100%)
Per USDA FoodData Central, unsalted butter contains approximately 81% fat, 16% water, and 3% milk solids by weight. Oil is 100% fat. When you replace 1 cup of butter with 3/4 cup of oil, you’re adding roughly the same amount of fat — the water that butter would have contributed is missing, but most moist batters don’t need it.
In very dry doughs or recipes where butter’s water helps create steam (like croissants or puff pastry), this missing water matters and the swap fails completely.
When the swap works well
These recipe types handle the butter-to-oil substitution without any significant quality loss:
- Muffins and quick breads (banana bread, zucchini bread, pumpkin bread)
- Brownies and bar cookies
- Oil-based cakes (carrot cake, chocolate cake with melted chocolate)
- Pancakes and waffles
- Pizza dough and focaccia
For these, the texture from oil is actually preferable — muffins stay moist longer, cakes have a finer crumb, and brownies are fudgier.
When the swap doesn’t work
Creamed butter recipes (most layer cakes, pound cakes): Creaming butter and sugar traps air — this is the primary leavening mechanism. Oil cannot trap air. Swapping all butter for oil in a creamed recipe produces a denser, flatter cake. King Arthur Baking recommends replacing no more than 25–50% of the butter with oil in creamed cakes, then creaming the remaining butter normally.
Pie crust, croissants, puff pastry: These require cold solid fat to create distinct layers. Oil simply coats the flour and produces a mealy, non-flaky texture.
Cookies: Most drop cookies depend on solid butter for spread control and structure. All-oil cookies spread excessively and can be greasy.
Choosing the right oil
| Oil | Best for |
|---|---|
| Canola oil | Neutral flavor; works everywhere |
| Vegetable oil | Neutral; good all-purpose |
| Light olive oil | Slightly fruity; good in citrus, chocolate, savory bakes |
| Coconut oil | Adds coconut flavor; solidifies at cool temps |
| Avocado oil | Mild flavor; high smoke point |
Extra-virgin olive oil has a pronounced flavor that can dominate baked goods — use it only when the flavor is welcome (Mediterranean-style breads, citrus cakes, savory muffins).
By weight
By weight, the conversion factor is slightly different from 3:4 because a cup of oil weighs less than a cup of butter (approximately 218 g vs. 227 g per cup for vegetable oil). To convert butter weight to oil weight, multiply by 0.71:
| Butter (g) | Oil (g) |
|---|---|
| 50 g | 36 g |
| 100 g | 71 g |
| 113 g (1 stick) | 80 g |
| 227 g (1 cup) | 161 g |
Source derived from USDA fat content data and King Arthur Baking weight chart.
What the missing water means for texture
When you swap butter for oil using the 3:4 ratio, you’re adding approximately the same amount of fat — but omitting the 16% water that butter would have contributed. This water matters in two ways:
-
Steam: In croissants, laminated doughs, and puff pastry, butter’s water turns to steam during baking, pushing apart the layers. Oil has no water and cannot create this steam — the dough will bake flat and greasy rather than flaky. Do not substitute oil for butter in laminated doughs.
-
Gluten development: Water develops gluten. Butter’s water content lightly develops gluten as you cream or mix. Oil’s lack of water means slightly less gluten development, which makes the crumb of oil-based muffins and quick breads slightly more tender. This is usually a benefit, not a problem.
For very dry doughs where moisture content is finely tuned — certain shortbreads, sablés, and Viennese cookies — omitting butter’s water will noticeably change the texture. Stick with butter for these.
Worked example: banana bread
Original recipe uses 1/3 cup (76 g) melted butter.
Oil conversion: 3/4 × 1/3 cup = 1/4 cup oil (or 54 g by the 0.71 weight factor).
Because banana bread uses melted butter (not creamed), the 1:1 swap of the same volume also works and produces a slightly moister loaf. Either approach is valid; the 3:4 rule is safer for most bakers who want to match the original recipe’s fat content precisely.
Vegan butter vs. oil in baking
Plant-based butters (Miyoko’s, Earth Balance, Country Crock Plant Butter) are formulated to mimic dairy butter’s fat-to-water ratio and can replace dairy butter 1:1 in most recipes — including creamed recipes where oil would fail. Use the same amount by weight or volume. The baking behavior is nearly identical; flavor differences depend on the specific product.