I made a little bread calculator that uses bakers percentages to scale a recipe up/down, calculate final hydration, dough weight and number of boules/pizzas.
It's a web app so it'll work on iOS, Android and desktop: http://brdclc.com/
You can scale by changing the flour value or the desired dough weight. It also appends the values you use to the URL, so you can share or bookmark a recipe, e.g. http://brdclc.com/?F=1000&W=75&S=2&L=20&LH=100
I know a lot of people use their own spreadsheets, keen to hear any feedback—especially on math or desired functionality.
I'm considering removing the ability to edit the final dough weight in favor of adding the ability to set number of loaves you'd like to make. Does anyone scale up by desired dough weight? Would adjusting the flour and seeing the dough weight scale accordingly suffice?