Psu calculators are only pas accurate as a) whomever is supplying the data on their end and b) how much data you supply. So what you need and what's recommended are often (almost always) different.
I don't go by actual used wattage, ever. I always go by absolute maximim possible. That includes any OC . Most gaming loads on a psu are 60-70% of that maximum, and psus prime area for thermals, power outputs, efficiency is in the 50-70% bracket. So taking absolute maximum, add a little headroom, like 50-100w, and that'll put gaming loads right where the psu likes them.