Butter ↔ Margarine

Margarine and spreads usually contain less fat and more water than butter, so a straight swap changes your dough. This calculator scales the amount so the fat in the recipe stays the same, and tells you how much liquid to take out.

How the calculation works

The calculation balances fat: margarine = butter × butter fat % / margarine fat %. In baking it's the fat that gives tenderness, flakiness and flavour, so that's the quantity worth preserving. The extra weight of margarine over butter is mostly water, which you should take away from the milk or water in the recipe.

Inputs: Butter is the weight in grams your recipe calls for (one US stick is about 113 g); Butter fat content defaults to 82.5%, typical of European-style butter, while US butter must contain at least 80% fat; Margarine or spread fat content comes from the label and defaults to 72%. The result gives the margarine weight, the fat in the substitute and how many grams of liquid to remove, or add if the margarine is richer than the butter.

Spreads under 60% fat are not recommended for baking: they hold a lot of water and emulsifiers, which make doughs wet and dense. Keep those for toast.

Worked example

Your recipe needs 200 g of 82.5% butter and you have a 72% spread. Fat in the butter: 200 × 0.825 = 165 g. Spread needed: 165 / 0.72 = 229.2 g. That's 29.2 g more, almost all of it water, so use about 29 g less milk or water in the dough. If the recipe has no liquid to cut, as in shortbread, choose a baking margarine with at least 80% fat instead.

Things to keep in mind

• For pastry, pie crust and shortbread, look for stick margarine labelled for baking with 80% fat; in the US, products sold as “margarine” must have at least 80% fat, while tubs labelled “spread” have less.
• Use the fat percentage on the actual packages. An 80% and an 82.5% butter give slightly different results.
• The swap can't recreate butter's flavour. In cookies or shortbread, where butter taste carries the recipe, you'll notice the difference.
• Margarines melt at a different temperature from butter, so dough may handle differently when rolling. Chill it a little longer.
• The calculation also works the other way: if the margarine has more fat than the butter, the calculator tells you how much liquid to add.