What can you do with this calculator?
You can calculate how long it takes until you have enough resources to bild something particular. So you can do without using your brain for calculating. The result is exaxt by minutes.

Example 1
You want to build a shipyard ant the next step costs 1600 metal, 800 crystal and 400 deuterium. You actually have 1234 metal, 543 Crystal and 100 deuterium. Your production per hour is 798 metal, 434 Crystal and 80 deuterium. you type it in the calculator and you see that you have enough resources for your shipyard in 3 hours and 45 minutes.

Example 2
You want to build an Espionage Probe. Only crystal is needed to build it. So in this case you only type the values for crystal and let the other fields free.