A power supply calculator is only as good as the numbers that you put into it. Some parameters are unknown, and unknowable.
If you are looking at a quality psu, like XFX, Seasonic, PC P&C, Corsair, or Antec, to name a few, you can use a simple rule of thumb:
Count how many pci-e 6 or 8 pin power connectors your graphics cards need in total, and get a psu with at least that number of connectors.
A quality unit will be able to deliver sufficient power to all the connectors, with enough left over to handle the rest of the system which is minimal by comparison.
If in doubt, get a larger unit; it will only use the power that is needed.