PSU Wattage Calculator?

Not that I know of. Usually the GPU is the main dictating factor, post your build and we can help. If a gaming or overclocking build the quality of psu is equally important, unfortunately wattage and efficiency rating are no measure of quality and you need independent reviews.
 
You Can just Post your specs and someone here Can tell you.

Generally Intel cpu + 1060 -> 400-500W
Intel CPU + 1070/Rx480 -> 450-550W
Intel CPU + 1080 -> 500-650W
Cpu + SLI -> 750-900W

Pretty much depends on the specific build but its an orientation for nee builds
 
You also have to remember that, especially with high-end graphics cards that need auxiliary power, the PSU wattage is not the only important factor. Amps on the +12v rails is equally important, if not more so.

Wattage calculator sites don't mention that so it's best to post your system specs.