You should be able to get a decent idea of expected output and fat percentage by looking at the nutrition label and doing a bit of math. US butter is typically

You should be able to get a decent idea of expected output and fat percentage by looking at the nutrition label and doing a bit of math. US butter is typically 80% fat, European ones may be 82-84% but if sold in the US might also just be using the brand name and US percentages. A nice primer: https://www.tastecooking.com/all-about-butter/ https://www.tastecooking.com/all-about-butter/ Regarding the "always unsalted" advice in there, I've seen discussion from high level cooks in the past few years of "just get salted; it keeps better and when we actually tested recipes it made no difference."