While the Newegg PSU Calculator is excellent for math, it cannot account for quality. Not all PSUs are created equal.
A cheap, generic "800W" power supply from a no-name brand might not actually be able to deliver 800W on the 12V rail (where your CPU and GPU get their power). It might be a fire hazard. newegg psu calculator
After getting your target wattage (+buffer), search Newegg with these filters: While the Newegg PSU Calculator is excellent for