Yet another calculator - Phazulator
Yeah, another 1. If ya find it useful - Enjoy! If not (I don't) don't worry about it. And it is phone friendly.h
Enter a desired amount and percentages for the other stuff (as noted) - It'll give a final weight and hydration, and of course how much to scale (for both preferment and final dough.
11-24-20 - fixed math (and logic)
11-26-20 - minor visual additions
11-30-20 - something bugged me so I fixed it
12-6-20 - slightly different approach