Free Butter Weight to Volume calculator with clear step-by-step results.
Butter is sold by weight in most of the world and measured by volume in US recipes. Dividing weight by density gives volume, and because chilled, softened and melted butter have measurably different densities the state you are working with is part of the conversion.
Volume from weight
Millilitres = grams / density (0.911 g/ml chilled)
US cups
Cups = millilitres / 236.588
Creaming or softening does not change the fat itself, but packed soft butter excludes the air gaps that chilled cubes leave, so a measured cup holds slightly more mass.
In the US, yes - a quarter-pound stick is 113.4 g or 8 tablespoons. European blocks are usually 250 g and are not divided the same way.