Use sour cream instead of buttermilk at 1:1 (thin with a little water). Buttermilk and sour cream do similar work in a recipe, but they are not identical, and the ratio is what makes the swap succeed. This guide gives the exact ratio, an equivalence table for every amount you will need, what changes in the finished dish, and when you should not make the swap at all. All ratios on this page come from the CookScale substitution data, and every result is approximate; taste the dish before serving, and adjust the seasoning if the swap changes the flavour.
Buttermilk to Sour cream: equivalence table
The table below scales the ratio — 1:1 (thin with a little water) — to every amount you will need, from a quarter of a cup up to three cups. Use the row that matches your recipe, and do not guess the scaling in your head, because a small error in the ratio grows with the size of the recipe.
| Buttermilk needed | Sour cream | Water (to thin) |
|---|---|---|
| 1/4 cup | 1/4 cup | 1 tsp |
| 1/2 cup | 1/2 cup | 2 tsp |
| 1 cup | 1 cup | 1 tbsp |
| 2 cups | 2 cups | 2 tbsp |
| 3 cups | 3 cups | 3 tbsp |
When a recipe calls for an amount that is not in the table, scale the ratio proportionally: work out how many cups of buttermilk the recipe needs, then multiply the ratio by that number. For a single cup, the ratio is exactly as stated; for half a cup, halve it; for two cups, double it. Keep the recipe scaler open while you cook, and you can scale the whole recipe, including the substitution, in one step.
What changes when you use sour cream instead of buttermilk
Sour cream is thicker and richer than buttermilk, so the swap makes the result more indulgent. In a cake, the sour cream adds fat and moisture, giving a denser, moister crumb that stays fresh for longer, which suits a rich chocolate cake or a coffee cake. In a biscuit, the sour cream gives a flakier, more tender result, because the fat shortens the dough. The flavour is similar, because both are cultured and tangy, and the acid activates the baking soda in exactly the same way, so the rise is the same. The main change is the thickness: sour cream is much thicker than buttermilk, so a batter made with sour cream may be stiffer, and it usually needs thinning with a little water. In a dressing, sour cream gives a thicker, richer result, which suits a baked potato topping better than a pourable dressing.
When not to substitute buttermilk with sour cream
Do not use plain milk — without acid, baking soda will not activate and the bake can taste soapy. That rule is the most important part of this page, because a substitution that works in one recipe can fail badly in another. Buttermilk does a specific job in each recipe, and the swap only works when the substitute can do the same job. In a recipe where buttermilk is the main structure — where it holds the bake together, or where its flavour is the point of the dish — the substitute will not do, and it is better to wait until you have the real ingredient, or to choose a different recipe. In a recipe where buttermilk is a supporting ingredient, where it adds moisture, richness or flavour but does not carry the dish, the swap usually works well. The test is simple: if removing the buttermilk would ruin the recipe, do not substitute it; if the recipe would still work without it, the substitute is probably safe.
Why this swap works
The acid in buttermilk activates baking soda and tenderises crumb; any acidic milk works the same way. That is the principle behind the swap: the substitute does the same chemical or structural job as the original, even though it looks and tastes different. The acid in an acidic substitute activates baking soda, the fat in a fatty substitute shortens a dough, and the liquid in a liquid substitute hydrates the flour. When the substitute does the same job, the swap works; when it does a different job, the swap fails. The ratio on this page is the amount that makes the substitute do the same job as the original, and it is worth following exactly, rather than guessing, because a small error in the ratio changes the job the substitute does.
Worked examples: buttermilk to sour cream in real recipes
1. A sour cream chocolate cake
A chocolate cake needs a cup of buttermilk, so use a cup of sour cream, thinned with a tablespoon of water. The sour cream gives the cake a denser, moister crumb that stays fresh for longer, which suits a rich chocolate cake, and the acid activates the baking soda, so the cake rises just as well. Whisk the sour cream and water together until smooth, pour the mixture into the batter exactly where the buttermilk would have gone, and bake the cake as usual, adding a minute or two if the crumb needs it.
2. Sour cream biscuits for breakfast
A batch of biscuits needs two cups of buttermilk, so use two cups of sour cream, thinned with two tablespoons of water. The sour cream gives the biscuits a flakier, more tender result, because the fat shortens the dough, and the acid helps them rise tall. Use the sour cream cold, straight from the fridge, so the butter stays cold in the dough, and work quickly, because warm dough makes flat biscuits.
3. A baked potato topping with sour cream
A baked potato topping for four needs a cup of buttermilk, so use a cup of sour cream, thinned with a tablespoon of water. The sour cream gives the topping a thicker, richer texture than buttermilk, which suits a baked potato, and the tang is the same. Whisk the sour cream and water together, stir in the chives and seasonings, and spoon the topping over the hot potatoes just before serving.
How to make the swap
Measure the sour cream cup for cup, exactly as you would the buttermilk, and thin it with a little water first: a tablespoon of water per cup of sour cream is usually enough, whisked together until the mixture pours like buttermilk. Use full-fat sour cream if you have it, because low-fat sour cream is thinner and less rich. Stir the thinned sour cream into the recipe exactly where the buttermilk would have gone, and do not change anything else. For a cake, the extra richness is an advantage, so the bake may need a minute or two longer in the oven. For a dressing, thin the sour cream a little more, so the dressing pours easily.
Common mistakes
The most common mistake is using sour cream without thinning it, which makes the batter too stiff and the bake too dense. Thin it with a little water first. The second mistake is using low-fat sour cream, which is thinner and less rich, and can make the bake watery; use full-fat sour cream if you can. The third mistake is heating sour cream too quickly in a sauce, which makes it split and turn grainy; keep the heat low and stir constantly. Finally, do not use sour cream in a recipe where the thinness of buttermilk matters, such as a light pancake batter, because sour cream is much thicker and the batter will be heavy.
Frequently asked questions
Can I substitute sour cream for buttermilk 1:1?
Yes, sour cream replaces buttermilk cup for cup, but it usually needs thinning with a little water first: a tablespoon of water per cup of sour cream is usually enough. Sour cream is much thicker than buttermilk, so a batter made with unthinned sour cream will be too stiff and the bake too dense.
Is sour cream richer than buttermilk?
Yes, much richer. Sour cream has more fat than buttermilk, so a cake made with sour cream has a denser, moister crumb that stays fresh for longer. The extra richness suits a chocolate cake or a coffee cake, but it can make a light sponge too heavy, so use it where the richness is an advantage.
Does sour cream activate baking soda like buttermilk?
Yes. Sour cream is acidic, just like buttermilk, so it activates baking soda in exactly the same way, giving the bake its rise and its tender crumb. The acid in sour cream is what makes it such a good substitute, and the bake will rise just as well as it would with buttermilk.
Should I use full-fat or low-fat sour cream?
Full-fat sour cream is better for baking, because it is richer and thicker, and it gives a moister crumb. Low-fat sour cream is thinner and less rich, and it can make the bake watery. If you only have low-fat sour cream, use it without thinning, because it is already thinner than full-fat.
Can I use sour cream in a buttermilk dressing?
Yes, and it gives a thicker, richer dressing, which suits a baked potato topping or a dip. For a pourable dressing, thin the sour cream with a little more water, so it pours easily. The tang is the same as buttermilk, so the flavour is very close, and the dressing stays fresh for longer.