Here is a Google spreadsheet for calculating sourdough hydration, starter quantity, etc.
Values are entered in the green cells. You should not be able to enter data in the red cells. These are calculated values.
For starter, enter the flour quantity and desired starter hydration, and it will calculate the water quantity to use.
For dough, enter the flour weight and the values for water, starter and salt in baker's percentages. The spreadsheet will calculate the weights and volumes of water and flour in cups.
At the bottom are total flour and water weight, dough weight and dough hydration.
Except for the volume (cup) measurements, the spreadsheet is "weight agnostic". You can use any unit of weight: grams, ounces, pounds, etc. The cup measurements are based on grams. In cell F2 you can enter the weight of one cup of flour. The spreadsheet will display cups next to the flour and water weights.
This can be used with yeasted bread as well. Manually adjust the baker's percentage value in cell B9 until cell C9 gives the weight of the proofed yeast (water + yeast weight).
You should get an error message if you try to enter data in protected cells. As the creator of the spreadsheet it is not possible for me to test cell protection because I always have permission to change protected cells.
Please report any errors or problems, particularly with cell protection, here.