The calculator has been improved a lot but it still need some love.
For instance, the default Relative Dielectric Constants, Er is 4.6. But there is no material that has this value. However the FR4 (which is the first thing in that list, and I believe could be the default, is 4.5 in the list). So, from where this 4.6 comes? Also, the items on this list could be better formatted, like Capitalized, maybe with a monospaced font or a column for the value and another for the Name of it. Also, the first thing could be the Item name, not the value, if using 2 columns, of course.
Input fields could also have a tooltip, since here, we are seeing some items being represented by their constant which sometimes are Greek letters. But for someone (like me), they may not be clear and having a Greek letter alone is not helpful so it is harder to look for backup info on Google. Also, there are different places (linke in the PCBNew that have different symbols, sometimes a Latin character instead of the Greek letter. It would be easier to understand if those constants could have the same name/symbol everywhere.
Here is an example of a different name for the same constant.
Also, PCBNew could have a link/button to the calculator, to launch it using current pcb settings so it would be faster to calculate stuff to the current board.
Another thing that could happen is that the popup windows could be wide enough to at least show the whole title visible.
