how much wattage do I need


Do from all of my research a 600w psu is all I need for a 1080 ti. However, I plan on overclocking it a far as it'll go so I know I'm going to need a bigger one. But just how much bigger? I've used a few different psu calculators and a couple are saying that with the overclock I currently have on my cpu along with the other things in my system that draw power that I'll need just a little above 600w so a 750w is recommended, however on other calcs it says I'll need a whopping 1200w and that doesn't seem right. I would naturally assume for a pascal card that 750w is perfect, however, can I actually get away with my current 600w or can o do lower than or do I need higher than a 750w? The 1080 ti cards I'm looking at use 2x8pin. I'm looking at either the Zotac Mini 1080 ti or the amp extreme 1080 ti since I can get one for $800 and the other for $850