Here is a table to help batch spargers plan their brewday. The table gives the amount of water required to mash in with a 1.25 qt./lb. (2.6 L/kg) mash thickness and how much sparge water would be required to rehydrate the grist to that thickness. It also gives the volumes of wort that would be collected with one or two additions of sparge water. Finally, it gives the volumes of additional water to add to collect either 6.0 gallons or 6.5 gallons of pre-boil wort when sparging once.
This chart allows batch spargers to look up how much water to heat during the brewday and lets them estimate how long of a boil time to plan for. All the numbers were generated on a spreadsheet. If you are a batch sparger, you can easily make your own spreadsheet that can be altered to account for different mash thickness, different target pre-boil wort volumes, the presence of dead spaces in your lauter tun or other variables.
The numbers in this chart are in English units. I’ll post the metric equivalent in the next few days.