How to convert oil to butter
Butter and oil are not interchangeable one-for-one. Butter is roughly 80% fat and 20% water plus a little milk solid, while cooking oil is close to 100% fat. To keep the same amount of fat in your recipe, you have to add more butter than the oil it replaces. The standard baking substitution is:
- Oil → Butter: multiply the oil amount by 1.25 (5/4). Example: 1/4 cup oil = 5 tablespoons butter.
- Butter → Oil: multiply the butter amount by 0.75 (3/4). Example: 1 cup butter = 3/4 cup oil.
The ratio works on any measure — cups, tablespoons, milliliters, or grams — because it converts the fat content, not the density. The calculator above also shows the result in tablespoons and approximate grams so you can measure whichever way is easiest.
Why the ratio isn't 1:1
If you swapped 1 cup of butter for exactly 1 cup of oil, you would actually be adding about 25% more fat, because that cup of butter was only ~80% fat to begin with. In sauces and sauté that extra richness rarely matters, but in cakes, muffins and cookies it changes how the batter spreads and how tender the crumb is. Scaling by 0.75 (or 1.25 the other way) matches the fat and keeps the recipe balanced.
Handy reference points
- 1 stick of butter = 1/2 cup = 8 tbsp = 4 oz = 113 g
- 1 cup butter (227 g) → 3/4 cup oil (about 163 g)
- 1 cup oil → 1 1/4 cups butter (about 284 g, or 2 1/2 sticks)
- 1 tbsp butter → about 2 1/4 tsp oil
Melted vs. solid butter
When you replace oil with butter in a batter that's mixed by hand or whisk, melt the butter first — oil is liquid, so melted butter mimics its behavior most closely. If a recipe relies on creaming solid butter and sugar for lift (many cakes and cookies do), switching to oil removes that aeration and gives a denser, moister result. That's a texture change to expect, not an error in the conversion.