Match the fat, not the volume
Butter is about 80% fat and 20% water and solids; oil is pure fat. So you replace butter with a little less oil, and oil with a little more butter. The working ratio is 3 parts oil to 4 parts butter.
Butter to oil, by common amount
| Butter | Oil (3/4 of the butter) |
|---|---|
| 1 tbsp | 2¼ tsp |
| 2 tbsp | 1½ tbsp |
| ¼ cup (4 tbsp) | 3 tbsp |
| ½ cup (8 tbsp) | 6 tbsp |
| ¾ cup | 9 tbsp (½ cup + 1 tbsp) |
| 1 cup | ¾ cup |
To go the other way, multiply the oil by 1⅓: ½ cup of oil becomes ⅔ cup of butter.
When the swap works, and when it doesn't
- Oil is better for muffins, quick breads, brownies and oil-friendly cakes. It stays liquid, so crumb comes out moist and tender.
- Butter is better for cookies, shortbread and anything creamed for rise. Its water and milk solids build flavor and structure.
- Do not swap where solid, cold butter does the work: laminated pastry, pie crust, buttercream or a sauce you cream. Oil can't hold that structure.
- Calories barely move. Both are almost all fat, so a swap changes texture far more than it changes the calorie count.
Common questions
What is the butter to oil ratio for baking?
Use about three parts oil for every four parts butter, roughly 3 to 4 by amount. To replace 1 cup of butter, use about 3/4 cup of oil. Going the other way, 1 cup of oil is replaced by about 1 and 1/3 cups of butter.
Why is it not a 1 to 1 swap?
Butter is only about 80% fat; the rest is water and milk solids. Oil is 100% fat. Matching the fat means using less oil than butter, which is where the 3 to 4 ratio comes from.
Does swapping butter for oil change the result?
Yes. Oil keeps cakes, muffins and brownies moist and tender because it stays liquid. Butter gives flavor and structure, so it wins for cookies, shortbread and anything you cream for lift. Do not swap in recipes where solid butter is the point, like laminated pastry.
