Indicate the desired quantity of loaves and an individual gross weight, as well as the few other vitals, and this form will calculate the weight of subsequent ingredients for the main dough as well as the weight of levain. The levain is assumed as a build of equal parts of bread flour and water (100% hydration).
Please let me know if and how this app can be improved! (I know, it is not really an app but a mobile-ready webpage. There is nothing to download and install.)