Do I Really Need to Use Unsalted Butter?

TL;DR 1 stick of salted butter (8 tbsp) has about 1/3 tsp of salt.

Maybe the same thing happens to you: you want to bake something. The recipe calls for unsalted butter. You have all the other ingredients. You have salted butter. You just don’t have unsalted butter. You look at the recipe. It calls for salt. Are you really going to go to the store and get unsalted butter? Should you just use salted butter? Maybe it will end up too salty! Why do they do that anyway!? Since we don’t eat that much butter at this point, it’s kind of a pain to keep two kinds on hand just in case.

This happened to me recently, and I finally decided it’s time for me to figure out how much salt there is in salted butter.

One tablespoon (14g) of Kerry Gold butter (one brand we had on hand) has 100mg of sodium. One tbsp of Whole Foods organic salted butter (the other one we had) has 80mg of sodium. It seems like 90mg is a pretty good average guess. According to Rose Beranbaum’s blog, the National Dairy Council says that salted butter is 1.6-1.7% salt, which works out to 90mg of sodium.

One stick of butter = 8 tablespoons. At 14g/tbsp, that is 112g per stick of butter. Taking 1.65% of 112 gives 1.8g of salt. Most sources will tell you that a tsp of salt is 6 grams, so this is about 1/3 tsp. So you can use salted butter and reduce the salt you add… or, this guy on reddit suggests you just leave the recipe as is and the extra salt will enhance the flavor of your dish. For example, Senga commented on the Rose Beranbaum post, “I usually make my shortbread with salted butter. Last time I used unsalted and frankly I find it’s missing taste. Will go back to salted although real shortie should be made with unsalted.”

The other consideration: my recipe called for Kosher salt, which comes in larger crystals so that when you take 1 tsp there is more air. It weighs about 5g. But 1/3 tsp still comes in in the right ballpark. However, I think the salt is supposed to be a bit crunchy in the recipe and give you little “salt bombs,” so it’s reasonable to stick with unsalted butter and add in the Kosher salt. Rose B likes the scent of unsalted butter better, but I’m not sure it makes a difference in the final product.

When I worked this out, I didn’t have the NDC figure, so I took this approach: 1 stick of butter = 8 tbsp. At 90mg of sodium per tbsp, that is 720mg of sodium per stick. How much sodium is in a tsp of salt? Only part of salt is sodium; the rest is chloride. What part of salt (sodium chloride) is sodium? Let’s go back to high school chemistry: the atomic weight of sodium (Na) is 23, and chlorine (Cl) is 35.5. The total is 58.5. Dividing, the sodium is 23/58.5=.39, so salt is 39% sodium. You will see people say 40%, which is definitely close enough. 40% of one tsp of salt (6g) is 6×0.4=2.4g of sodium per tsp of salt. That is 2,400mg. 720mg of sodium in stick of butter divided by 2400 mg of sodium in a teaspoon of salt is 0.3… so a stick of butter is (again) about 1/3 tsp of salt. Checking online, people seem to say 2,300+ mg of sodium in a tsp of salt. Close enough!

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