Same fat, different form
Butter and oil both bring fat to a recipe, but butter is not pure fat. In the United States, butter must contain at least 80% milkfat; the rest is about 16 to 18% water and a little milk solids. Vegetable oils are 100% fat. To swap one for the other without changing the richness of the recipe, you match the amount of fat, not the volume.
The calculation
Butter to oil: fat = butter weight × fat content; oil volume = fat ÷ 0.92, the density of most vegetable oils.
Oil to butter: fat = oil volume × 0.92; butter weight = fat ÷ fat content.
The calculator also shows the water you can add back when replacing butter with oil, about 18% of the butter weight. It is optional: most recipes are fine without it.
Quick equivalents
| Butter | Oil |
|---|---|
| 1 tablespoon | about 2½ teaspoons |
| ¼ cup (½ stick) | 3 tablespoons + 1 teaspoon |
| ½ cup (1 stick) | about 6½ tablespoons |
| 1 cup (2 sticks) | about ¾ cup + 1 tablespoon |
Example
A recipe calls for 8 tablespoons (1 stick, 114 g) of butter. At 80% fat, that is 91 g of fat, or about 99 ml of oil, a little over 6½ tablespoons.
When the swap works
Oil works well in recipes where butter is melted or simply mixed in:
- muffins, quick breads, banana bread;
- brownies and many cakes, which become moister and stay soft longer;
- pancakes and waffles;
- sautéing and roasting.
It fails when solid butter has a structural role:
- creaming butter with sugar traps air for light cakes and cookies;
- pie crust, biscuits and scones rely on cold pieces of butter that create flaky layers;
- laminated doughs, such as croissants and puff pastry;
- buttercream and other frostings.
Choosing the oil
Neutral oils such as canola, vegetable or sunflower keep the original flavor. Olive oil suits savory dishes and some cakes. Coconut oil, solid below about 76 °F (24 °C), can replace butter in some creamed recipes but tastes of coconut unless refined. Flavor matters: butter brings a taste oil cannot fully replace, so a pinch of extra salt or a little vanilla can help in baking.