Measurements for substituting vinegar for cream of tartar?

Generally, you want to substitute the same amount of vinegar for cream of tartar in a recipe. However, the substitution of vinegar is usually used for whipping egg whites (where it helps to give volume) and not so much baked goods like sugar cookies.

From my understanding, cream of tartar is usually used with baking soda in cookie recipes as a leavening agent (it works in the same way baking powder would)- this works because they are both dry ingredients, so I'm not too sure if vinegar would be a good substitution. But if you want to, feel free to substitute the equal amount vinegar and see what happens- I would be wrong!!

If your recipe calls for baking soda as well, a better substitution would be baking powder- substitute both the baking soda and cream of tartar for the baking powder (this is what I usually do).

Hope this helps!