Butter to Oil Conversion Calculator

Why butter to oil isn't 1:1

Picture a stick of butter as three things pressed together: fat (80%), water (16%), and milk solids (4%). Only the fat does the job that oil does. So when a recipe calls for butter and you reach for oil, the question isn't “how much butter” but “how much of that butter was fat?”

The answer is 80% of its weight. A cup of butter (227g) carries 182g of fat, which is why the converted amount is 182g of oil: about ¾ cup plus 1½ tablespoons. This is where the folk “¾ cup rule” comes from. It's the same math, rounded down.

The part the ¾ cup rule skips: that cup of butter was also delivering 36g of water to your recipe. Swap in oil and the water vanishes, making batters stiffer and crumbs drier than the recipe author intended. The fix is simple, and this calculator does it for you: add the lost water back as milk or water with the wet ingredients.

The one thing no substitution recovers is the milk solids. They're what browns in the pan and gives butter bakes their nutty depth. Oil cakes are moister; butter cakes taste like butter. That trade is real and worth making with your eyes open.

Common conversions

The reference points worth memorising, for US butter (80% fat) to a neutral oil:

Going the other direction (a recipe calls for oil, you have butter)? Multiply the oil weight by 1.25 to get the butter amount, and reduce the recipe's other liquid by 16% of the butter's weight. The calculator handles both directions.

When the swap works (and when it doesn't)

Whether butter-to-oil survives the trip depends entirely on whether the recipe uses butter as a structural ingredient or just as fat.

Where oil shines: muffins, quick breads, brownies, and any cake built on the “mix wet into dry” method. These recipes use fat purely for tenderness and moisture, and oil delivers both, often better than butter. Oil-based bakes also stay soft for days because liquid fat doesn't recrystallise the way butterfat does.

Where it gets risky: creaming-method cakes. When a recipe says “cream the butter and sugar until light and fluffy,” that step is whipping millions of air pockets into solid fat, and those pockets are the cake's leavening scaffold. Oil can't hold air. The cake will still bake, but denser and flatter than intended.

Where it fails outright: cookies, pie crust, biscuits, scones, and anything laminated. Cookies need solid butter to control spread. Flaky pastry needs cold fat in discrete pieces that steam apart into layers. And lamination, the technique behind croissants, is physically impossible with liquid fat: the butter block must stay a distinct, plastic layer between sheets of dough. If that's your project, head to the laminated dough calculator and use real butter.

Enriched yeast doughs (brioche, challah, milk bread) sit in the middle: oil works mechanically, and the dough handles fine, but you lose the buttery flavour that's usually the point. The enriched dough calculator assumes butter; convert its output here if you need dairy-free.

Shortening, coconut oil, and other fats

The same fat-and-water math covers every common baking fat, which is why this converter handles nine of them. The key distinction isn't butter vs. oil; it's solid vs. liquid.

Shortening is 100% fat, zero water, zero flavour. It creams, it flakes, and it makes exceptionally tender cakes. Use 80% of the butter weight and add the water back. What you give up is browning and taste.

Coconut oil is the most butter-like of the dairy-free options because it's solid below 24°C (76°F). Solid, it can do butter's structural jobs: creaming, cutting into flour for pastry, holding cookie spread. Melted, it behaves like any other oil. Refined coconut oil is neutral; virgin carries coconut flavour.

Lard is the traditional pie-crust fat, and for good reason: its large fat crystals produce exceptional flake. Ghee is butter with the water and milk solids already removed, so it converts like an oil, not like butter, and it keeps some browned-butter flavour. Stick margarine mimics butter's 80/16 composition and swaps 1:1; tub spreads run far lower in fat and don't bake reliably.

Need the density of a fat for a volume conversion? The baking weight converter covers all of these and 50+ other ingredients.

The salt hiding in salted butter

Salted butter carries about 1.6% salt by weight, roughly ½ teaspoon per cup. Recipes developed with salted butter count on it. Swap in oil (or any unsalted fat) without compensating and the bake tastes flat in a way that's hard to diagnose: not bland exactly, just muted.

The fix costs nothing: when you replace salted butter, add the equivalent salt to the dry ingredients. The calculator computes it when you flip the “salted butter” toggle. One caveat: 1.6% is an industry average, and brands run anywhere from 1.2% to 2%, so treat the correction as a good default rather than a guarantee.

Frequently asked questions

How much oil equals 1 cup of butter?

About ¾ cup plus 1½ tablespoons (182g of oil for 227g of butter). Butter is roughly 80% fat, so you need 80% of the butter's weight in oil to match the fat content. Because butter is also ~16% water, add about 2½ tablespoons (36g) of milk or water back to the recipe to keep the moisture balanced. The popular ¾-cup rule is this same math, rounded down.

Can I use olive oil instead of butter?

Yes, with the same conversion as any oil: use 80% of the butter's weight. The consideration is flavour. Extra virgin olive oil carries grassy, peppery notes that suit savoury bakes, focaccia, and some rustic cakes, but can clash with delicate vanilla or fruit flavours. For neutral results in cakes and muffins, use light (refined) olive oil.

Can I substitute oil for butter in cookies?

Mostly no. Cookie structure depends on solid butter: it holds the dough's shape as it heats, then melts gradually to control spread. Swap in oil and the fat is liquid from the first minute in the oven, so the cookies spread flat and bake up greasy. If you must avoid butter in cookies, a solid fat like coconut oil or shortening preserves the structure far better than liquid oil.

Can I use shortening instead of butter?

Yes, and it's an excellent swap for flaky pastry and tender cakes. Shortening is 100% fat with no water, so use 80% of the butter's weight and add the lost water back as liquid. Two trade-offs: shortening contributes zero flavour, and it doesn't brown the way butter's milk solids do.

Do I really need to add the water back?

For small amounts (under half a cup of butter) the missing tablespoon of water rarely shows in the result, so it's optional. For larger amounts, yes: a cup of butter carries about 36g of water, and losing it makes batters stiffer and crumbs drier than the recipe intends. Add the correction as milk or water with the other wet ingredients.

Is melted butter the same as oil?

No. Melted butter is still 80% fat and 16% water, and it resolidifies as it cools. Recipes that call for melted butter already account for its water; swapping in oil 1:1 there over-delivers fat and under-delivers moisture, just like any other butter-to-oil swap. Use the converter for melted butter exactly as you would for softened.

Do I measure coconut oil solid or melted?

Measure it solid if the recipe uses a solid fat (creaming, cutting into flour), then use it solid. Melt it only when the recipe expects a liquid fat. Coconut oil is 100% fat either way, so the weight doesn't change, but its physical state determines whether it can do a solid fat's structural job in the recipe.

How much salt is in salted butter?

About 1.6% of the butter's weight on average, though brands run anywhere from 1.2% to 2%. That's roughly ½ teaspoon of salt per cup (227g) of butter. When you replace salted butter with oil or another unsalted fat, add that salt back or the bake will taste noticeably flat.