Hong Life CalculatorsUnderstanding the butter to oil converter — concept and principle
Butter is not pure fat: it is an emulsion of milk fat with water and a little milk solids. Vegetable oil and ghee, on the other hand, are almost pure fat. This converter tells you how much oil (by weight and by volume) or ghee delivers the same amount of fat as a given weight of butter, which is the usual basis for swapping fats in muffins, quick breads, brownies and sautéing. Stick or block margarine sold for baking usually has a fat content similar to butter and is generally swapped by equal weight.
How it is calculated
- Vegetable oil (g) = butter × 0.8.
- Oil (mL) = butter × 0.8 ÷ 0.92, using a typical oil density of about 0.92 g/mL.
- Ghee or clarified butter (g) = butter × 0.82.
Input is butter in grams.
The principle
Butter typically contains about 80–82 % fat, around 16 % water and 1–2 % milk solids. In many countries butter must legally contain at least 80 % milk fat. Replacing 100 g of butter with 80 g of oil keeps the total fat the same, and the missing water (about 16–18 g) can be made up with a little extra liquid if the batter seems dry. Ghee is butter with the water and milk solids removed, so roughly 82 g of ghee carries the fat of 100 g butter. Oil is lighter than water, which is why its volume is larger than its weight.
Worked example
Default: 100 g butter.
- Oil by weight = 100 × 0.8 = 80 g.
- Oil by volume = 80 ÷ 0.92 = 86.96 mL.
- Ghee = 100 × 0.82 = 82 g.
| Butter (g) | Vegetable oil (g) |
|---|---|
| 25 | 20 |
| 50 | 40 |
| 75 | 60 |
| 100 | 80 |
| 125 | 100 |
| 150 | 120 |
| 200 | 160 |
How to read the result
The swap works best where fat is used melted: muffins, many cakes made by the "melted fat" method, brownies, pancakes and frying. It works poorly where solid butter traps air or forms layers, such as creamed cakes, shortbread, pie crust and laminated pastry; there the texture changes noticeably. Oil-based cakes stay moist longer but have less buttery flavour.
Common mistakes
- Swapping 100 g butter for 100 g oil, which adds about 20 % more fat.
- Using a low-fat spread instead of baking margarine; spreads contain much more water.
- Measuring oil in a cup when the recipe was converted in grams.
Frequently asked questions
Should I use unsalted or salted butter values?
The fat content is similar; with salted butter, reduce added salt slightly when converting back from oil.
Can I replace oil with butter?
Yes, reverse it: divide the oil weight by 0.8 to get butter.
Is ghee the same as clarified butter?
Both remove water and milk solids; ghee is usually cooked a little longer, giving a nuttier flavour.
Sources: USDA FoodData Central — butter, salted and unsalted (composition). · Harold McGee, On Food and Cooking (Scribner) — butter and cooking fats.