Oil to Butter Converter

Background.

How much oil replaces a cup of butter? Matched on fat, about 184 g — a little over five-sixths of a cup, or 13½ tablespoons. Not a full cup, and not the three-quarters of a cup that most substitution charts give.

The reason is composition. USDA's analysis of salted butter finds 81.11% fat and 16.17% water, the rest being milk solids and salt; a liquid cooking oil is all fat and no water. So a gram of oil carries nearly a quarter more fat than a gram of butter, and taking butter out of a recipe also takes out the water it was carrying. A cup of butter weighs 227 g on USDA's portion table and holds 184.12 g of fat. Oil weighs 218 g to the cup, so the 184.12 g of oil that carries the same fat fills 0.84 of a cup.

Three ways of matching are offered. Matching the fat is the default and leaves the recipe's fat unchanged. Matching the weight swaps gram for gram and adds fat when oil goes in. The traditional three-quarter-cup rule is a rule of thumb stated in volume; it is convenient, and on a cup of butter it delivers about 11% less fat. Whichever you choose, the other two answers are shown beside it.

Arithmetic cannot settle whether the swap will work. Oil suits cakes, muffins, quick breads and brownies, where the fat only has to be fat, and often makes them moister. It fails wherever butter has to be solid: creamed with sugar to trap air, or cut cold into flour for pie crust, biscuits, scones and laminated pastry.

What is oil to butter converter?

An oil-for-butter substitution exchanges two fats of different makeup, and two numbers from USDA FoodData Central decide the arithmetic. Salted butter, entry 173410, has 81.11 g of fat and 16.17 g of water per 100 g. Canola oil, entry 172336, has 100 g of fat and no water. Volume conversions need each fat's weight per cup, which USDA gives as 227 g for butter and 218 g for oil. Against the US cup, defined as exactly 236.5882365 mL, those correspond to densities of about 0.9595 g/mL for butter and 0.9214 g/mL for oil. Most liquid cooking oils are close enough to canola that the same figures serve for sunflower, corn or light olive oil.

How to use this calculator.

1. 01Choose the direction: the recipe wants butter and you want to use oil, or the recipe wants oil and you want to use butter. The second adds water to the recipe rather than removing it.
2. 02Enter the amount from the recipe and its unit. Sticks are accepted only when the recipe's fat is butter, since oil is not sold in sticks; a stick counts as USDA's 113 g.
3. 03Keep the basis on fat unless you have a reason to change it. Choose weight for savoury cooking where exact fat matters little, or the three-quarter-cup rule if you want to compare with a recipe that used it.
4. 04Measure out the gram figure if you have a scale; otherwise use the cups or tablespoons, which use the replacement fat's own density.
5. 05Look at the change in water. The same few tablespoons are a larger share of the liquid in a recipe that has little milk, egg or fruit, so that is where the change is most likely to show.

The formula.

The recipe's amount is first turned into grams using the density of the fat the recipe names: a cup of butter is 227 g, a cup of oil 218 g, a tablespoon a sixteenth of the cup and a teaspoon a forty-eighth, and an ounce 28.35 g. On the fat basis the replacement weight is g_sub = g_orig × fat_orig ÷ fat_sub, so butter to oil multiplies by 0.8111 and oil to butter divides by it, and the fat change is exactly zero. On the weight basis g_sub = g_orig. The traditional rule works in cups: cups of butter × 0.75 gives cups of oil, or cups of oil ÷ 0.75 gives cups of butter, converted back to grams at the replacement fat's cup weight. The water change is g_sub × w_sub − g_orig × w_orig, with water fractions of 0.1617 for butter and 0 for oil, so it is negative when butter leaves the recipe and positive when it comes in. USDA also publishes a 14 g oil tablespoon, but sixteen of them make 224 g against its own 218 g cup; the cup is used because it implies a density typical of cooking oil, and every spoon is derived from it.

A worked example.

Frequently asked questions.

References& sources.

1. [1]U.S. Department of Agriculture, Agricultural Research Service. FoodData Central, SR Legacy entry FDC ID 173410, "Butter, salted"; retrieved 30 July 2026 through the FoodData Central REST API endpoint /v1/food/173410. The source of butter's composition and density on this page: total lipid (fat) 81.11 g per 100 g from 580 data points; water 16.17 g per 100 g from 7 analytical samples spanning 15.8 to 16.61 g; portions 1 cup = 227 g, 1 stick = 113 g, 1 tablespoon = 14.2 g, 1 pat = 5 g.
2. [2]U.S. Department of Agriculture, Agricultural Research Service. FoodData Central, SR Legacy entry FDC ID 172336, "Oil, canola" (low erucic acid rapeseed oil); retrieved 30 July 2026 through the FoodData Central REST API endpoint /v1/food/172336. The source of oil's composition and density: total lipid 100 g per 100 g from 8 data points, water 0 g per 100 g, and portions 1 cup = 218 g, 1 tablespoon = 14 g, 1 teaspoon = 4.5 g. The cup is used as this page's density anchor and the separately published tablespoon is documented as inconsistent with it (16 x 14 = 224 g against a 218 g cup).
3. [3]United States Code, Title 21, Section 321a — "Butter" defined (enacted 4 March 1923, 42 Stat. 1500); retrieved 30 July 2026 from the Cornell Legal Information Institute's reproduction of the US Code. Quoted for the statutory floor reported beside USDA's measured milkfat mean: butter is the food "made exclusively from milk or cream, or both, with or without common salt, and with or without additional coloring matter, and containing not less than 80 per centum by weight of milk fat, all tolerances having been allowed for."
4. [4]National Institute of Standards and Technology. NIST Special Publication 811, 2008 edition — Guide for the Use of the International System of Units (SI). Table B.6 US customary capacity: cup exactly 236.5882365 mL, tablespoon 14.78676478125 mL, teaspoon 4.92892159375 mL, hence the exact identities 1 cup = 16 tablespoons = 48 teaspoons that this page uses to derive every spoon figure from the cup; Table B.8 avoirdupois mass: ounce exactly 28.349523125 g. The exact cup is also the instrument that resolves the two density conflicts documented on the page, by converting each published gram-per-cup figure into an implied g/mL.
5. [5]King Arthur Baking Company. Ingredient Weight Chart, current revision; retrieved 30 July 2026. Cited for the figure this page records as a conflict and does not use: "Vegetable Oil — 1 cup: 7 ounces / 198 grams", against USDA's 218 g. The chart's butter entry, "8 tablespoons (1/2 cup): 4 ounces / 113 grams", does agree with USDA's stick portion. The oil discrepancy is named in the output descriptions and in an FAQ, together with the implied-density test that resolves it, so a reader comparing this page against King Arthur's numbers can see exactly why they differ.