Butter to Oil Converter
Enter the amount in your recipe and we will convert it, in grams and millilitres.
Answer
80 g of oil, which is about 87 ml
Quick reference
Butter is roughly 80% fat and 20% water, so you need less oil than butter. That missing water is why the swap changes the result.
- Oil has no water in it, so cakes come out moister and slightly denser, and biscuits spread more.
- Creaming butter and sugar traps air. If the recipe starts by creaming, oil cannot do the same job, expect a closer crumb.
- For pastry, shortbread and anything that needs to hold its shape, do not swap butter for oil.
- For frying and roasting, swapping is straightforward. Oil also takes more heat before it burns.
Source: Standard UK and US kitchen reference weights and manufacturer guidance · Reviewed 2026-09-10 · Guidance version 1.0.0
Reference and detail
Why you use less oil than butter
Butter is roughly 80% fat and the rest mostly water. Oil is pure fat. So 100g of butter is only about 80g of actual fat, and that is the amount of oil you need. Swap gram for gram and the result is greasy.
Where the swap works
Frying, roasting and any recipe where the butter is simply melted are straightforward, and oil takes more heat before it burns. Loaf cakes, muffins, brownies and carrot cake are often better with oil, moister, and they keep longer.
Where it does not
Anything that creams butter with sugar depends on air being beaten into solid fat, and oil cannot hold air. Pastry, shortbread, croissants and buttercream all rely on butter being solid and cold or on butter's flavour, so leave those alone.
Questions and answers
Questions about swapping butter for oil
Can I substitute oil for butter gram for gram?
No. Butter is roughly 80% fat with the rest mostly water, while oil is pure fat, so gram-for-gram oil will make a recipe greasy.
Enter the amount of butter in the calculator above to see how much oil actually replaces it.
Which bakes work well with oil instead of butter?
Loaf cakes, muffins, brownies and carrot cake generally turn out moister with oil and keep longer. Frying and roasting, where the butter is simply melted for cooking, also swap easily.
Why can't I use oil in pastry or shortbread?
Those bakes rely on solid, cold fat holding its shape and, in creamed mixtures, on air being beaten into that solid fat, something liquid oil cannot do. Leave butter in for pastry, shortbread, croissants and buttercream.