Baking with Olive Oil: Replacing Butter the Right Way

Key takeaways

The common conversion replaces butter with about three quarters of its volume in olive oil; on a gram-to-millilitre basis the same chart uses a factor of 0.78 — so 100 grams of butter becomes 78 millilitres of oil.
The reason is in Swiss law: butter is an emulsion of water in milk fat with at least 820 grams of milk fat per kilogram, while olive oil is pure fat.
The overlooked half of the calculation: along with the butter, 16 to 18 per cent water leaves the recipe, and no conversion chart replaces it.
Liquid fat traps almost no air. The swap works for pound cakes, muffins, brownies and focaccia, and fails for puff pastry, shortcrust and anything that begins with creamed butter.
At 180 degrees the phenolic content of three monovarietal oils stayed unchanged, but the predominant aroma compound lost 94 to 95 per cent. A delicate oil is therefore enough for baking.

Swapping butter for olive oil in baking is not a one-to-one operation, and the reason is written into Swiss food law. The Federal Department of Home Affairs ordinance on foodstuffs of animal origin defines butter as «an emulsion of water in milk fat». Olive oil, by contrast, is pure fat. Replace gram for gram and you put more fat and less water into the batter than the recipe calls for — then wonder about the result. This article works the conversion through, says where it succeeds, where it fails, and which oil is worth using.

The number: three quarters

The best-known conversion chart is published by the North American Olive Oil Association. Important context: that is a trade association, and the page gives neither a source nor a derivation for its figures. Its volume table is a clean factor of 0.75: one cup of butter becomes three-quarters of a cup of oil, 100 millilitres of butter becomes 75 millilitres of oil, 500 becomes 375.

The same chart, however, also converts grams of butter into millilitres of oil — and that one uses a different factor, 0.78: 100 grams of butter gives 78 millilitres of oil, 500 grams gives 390. The two tables are not arithmetically consistent with each other. Pick one basis and say which; «the» factor does not exist.

Butter in the recipe	Olive oil (gram-to-millilitre basis, factor 0.78)	Rounded for the kitchen
50 g	39 ml	40 ml
100 g	78 ml	80 ml
125 g	97.5 ml	95 ml
200 g	156 ml	155 ml
250 g	195 ml	195 ml
300 g	234 ml	235 ml
500 g	390 ml	390 ml

Why it is not one to one: the arithmetic of butter

Article 73 of that Swiss ordinance requires butter to contain at least 820 grams of milk fat per kilogram, and salted butter at least 800. Swiss butter is therefore at least 82 per cent fat — the rest is essentially water and non-fat milk solids. Iowa State University Extension puts it in kitchen terms: «Butter is at least 80 percent fat and 16-18 percent water.»

From this the whole calculation follows: 100 grams of butter delivers roughly 80 to 82 grams of fat, while 100 grams of olive oil delivers 100 grams of fat. The ratio therefore sits at about 0.80 to 0.82 — in the same neighbourhood as the trade chart's 0.78 and 0.75. A caution about the reasoning: the North American Olive Oil Association states no such derivation. The figures are consistent with butter's composition; nobody claims they were derived from it.

The second half of the calculation is almost always overlooked: along with the butter, 16 to 18 per cent water also leaves the recipe, and none of the conversion charts replaces it. For 200 grams of butter that is a good 30 millilitres of liquid missing from the batter. In wet cake batters it hardly shows; in tightly balanced doughs it is worth keeping in view.

What actually changes in the batter

University of Illinois Extension describes the functions of fat in baking soberly. First: «Fat prevents flour from absorbing water» — which is why reduced-fat muffins and biscuits often turn out tougher, because the gluten develops more. Second, and this is the heart of the matter: «When baking with oils, little air is trapped in liquid fat compared to solid, creating a softer and chewier consistency.»

Iowa State University Extension describes the same mechanics in cookies: with 100 per cent liquid fat «very little air incorporates into the dough, resulting in denser, flatter cookies» than with solid fats. And the Illinois source names an explicit limit: substituting oil for solid fats «can cause pastries to be mealy rather than flaky».

Translated into a decision rule: the swap trades air for moistness. Where a recipe gets its structure from creamed butter, it loses that structure. Where it gets its quality from moisture and tenderness, it gains.

Works well	Works badly
Pound cakes, lemon and yoghurt cakes	Puff pastry and anything laminated, croissants
Muffins, banana bread, carrot cake	Shortcrust pastry and butter biscuits meant to be flaky
Brownies and chocolate cakes	Recipes that begin by creaming butter and sugar
Focaccia, olive bread, pizza dough, enriched yeast breads	Buttercream, icings, butter-based fillings
Biscotti, olive oil cake, crostata bases	Piped biscuits that must hold their shape

What has been measured in real cakes

Two peer-reviewed papers have actually studied the swap, and both deserve careful framing.

A Greek team led by A. Matsakidou compared, in «LWT – Food Science and Technology» (2010), Madeira cakes in which margarine was wholly or partly replaced by extra virgin olive oil. The replacement significantly affected the hardness and cohesiveness of the cakes, increased batter density and cake volume, and decreased weight loss during baking; aroma analysis found a wide range of volatile compounds originating either from the oil or produced during baking. Important: the comparator was margarine, not butter. The work shows that olive oil measurably changes crumb and volume — not how it fares against butter.

That second comparison is supplied by a paper led by Jean-Xavier Guinard in the «International Journal of Gastronomy and Food Science» (2020). A trained sensory panel described four dishes in which butter was replaced with extra virgin olive oil. For bakers the result is the best news in the whole subject: pasta and green beans each showed 14 significantly changed attributes, fish showed 9 — the cake only 5. Of four dishes, the cake was the one the swap changed least.

Which oil — and why not the most expensive one

Here there is a good, rarely told measurement. A Croatian team led by D. Klisović heated, in «Foods» (2024), 50 grams each of monovarietal extra virgin olive oil — Leccino, Istarska bjelica and Buža — in an open Pyrex dish in an air oven for one hour at 180 and at 220 degrees Celsius.

At 180 degrees the total identified phenolic content remained statistically unchanged in all three varieties. Only at 220 degrees did it fall, by about 47 per cent for Leccino and about 39 per cent for Istarska bjelica, while Buža remained unchanged.
Individual compounds nevertheless shifted markedly already at 180 degrees: one oleuropein aglycone isomer decreased by 65 to 67 per cent.
Aroma is the first casualty: (E)-2-hexenal, the predominant volatile, lost 94 to 95 per cent at 180 degrees and was almost completely degraded at 220. The phenolic change was variety-dependent, the aroma change primarily temperature-dependent.

One important limitation: what was measured was oil alone in an open dish, not oil dispersed in a batter. The percentages do not transfer to a cake.

What can still be drawn from it — as our reasoning, not as the study's finding: the polyphenols you buy a good oil for largely survive a normal baking temperature. The green, fresh aroma you pay the premium for does not. For the oven, then, a delicate or simply less aromatic extra virgin olive oil is the sensible choice; the assertive oil belongs on the salad and over the finished dish. For comparison, the smoke point ranges published by the North American Olive Oil Association: extra virgin olive oil typically 350 to 410 degrees Fahrenheit (about 177 to 210 degrees Celsius), refined olive oil 390 to 470 degrees Fahrenheit. A typical cake bakes at 170 to 180 degrees Celsius, below that range. More on why stability says more than smoke point in Cooking with Olive Oil, and more on the phenols in Olive Oil Polyphenols.

Three conversions for everyday baking

No new recipes — just the table above applied to three classics:

A pound cake with 200 grams of butter

Replace with 155 millilitres of olive oil. Because creamed butter no longer supplies the air, separate the eggs and fold in the whites at the end — the air then comes from the egg white instead of the fat. Around 30 millilitres of liquid are missing compared with butter; milk, yoghurt or lemon juice makes it up.

Brownies with 125 grams of butter

Replace with 95 millilitres of olive oil. This is the easiest swap of all, because brownies take their quality from density and moisture rather than from air — precisely the properties that liquid fat reinforces, according to the extension sources.

Shortcrust pastry with 250 grams of butter

Do not convert it. This dough lives on cold pieces of fat between layers of flour; with oil it turns mealy rather than flaky, as the Illinois source says. If you want an oil-based dough, use a recipe designed around oil from the start — an Italian crostata base, or a focaccia. Ideas in Swiss Recipes with Olive Oil.

Frequently asked questions

How much olive oil replaces 100 grams of butter?

According to the North American Olive Oil Association's chart, 78 millilitres — so about 80 in practice. That fits butter's composition: Swiss butter contains at least 820 grams of milk fat per kilogram, while olive oil is pure fat.

Why is the ratio not one to one?

Because, under Swiss law, butter is an emulsion of water in milk fat: at least 82 per cent fat, the rest mostly water. Swapped gram for gram, too much fat and too little water goes into the batter.

Do I have to replace the missing liquid?

The conversion charts do not. With 200 grams of butter, a good 30 millilitres of water leaves the recipe. Wet cake batters tolerate it; in tightly balanced doughs, make it up with milk, yoghurt or juice.

What is olive oil unsuitable for in baking?

For anything meant to be flaky, and anything that begins with creamed butter: puff pastry, croissants, butter biscuits, buttercream. University of Illinois Extension writes that substituting oil for solid fats can make pastries mealy rather than flaky.

Does baking destroy the polyphenols in olive oil?

At baking temperature, apparently not substantially: in a 2024 experiment, the total identified phenolic content of three monovarietal oils remained statistically unchanged after an hour at 180 degrees; only at 220 did it collapse in two of the three varieties. That said, oil was heated alone in an open dish, not in a batter — the figures do not transfer directly.

Is expensive extra virgin olive oil worth it for baking?

For flavour, barely. The same experiment shows that the predominant volatile, (E)-2-hexenal, loses 94 to 95 per cent at 180 degrees. The aroma you pay the premium for stays behind in the oven. A delicate extra virgin olive oil is enough; the best oil in the house belongs on the salad.

Does olive oil change a cake a lot?

Less than most people expect. A trained panel replacing butter with extra virgin olive oil across four dishes found only 5 significantly changed attributes in the cake — against 14 each for pasta and green beans.