One is for MAX watts, but what you want is the sustained, constant, working watts. You also have to consider the power loss from converning AC to DC. Most cheaper PSU are about 70% efficient. You'd want one that is 80% at least. Also, having more watts is better than equal or less to your needs. I use Antec since their ratings are "continuous power".
This would be right on the target for you, but it's a dual, not single rail.
550w Continuous Power
80 PLUS Bronze certified - up to 88% efficient
ATX12V version 2.32
Here's some more upscale.
https://www.amazon.com/Antec-EarthWatts-EA-650-BRONZE-Supply/dp/B004NNN7Q4/ref=sr_1_15?s=electronics&ie=UTF8&qid=1505170943&sr=1-15&keywords=antec+psu+power+supply
https://www.amazon.com/Antec-Current-HCG-620M-BRONZE-Modular/dp/B006TVQTFE/ref=sr_1_3?s=electronics&ie=UTF8&qid=1505170943&sr=1-3&keywords=antec+psu+power+supply
Hi all! I was wondering how you all calculate the total number of watts you'll need your PSU to deliver. I've come across the Newegg calculator, which calculates the watts of the CPU, Motherboard, Video Card, Memory, Optical Drive, HDD, and SDD. Does this mean that I need to buy a PSU that matches this calculation exactly? I believe my total was 435W; does that mean I need a 435W PSU, or should I go higher than that with something like a 450W PSU? Also, did the Newegg calculator leave out any components that I need to factor in? Like a CPU Cooler?
Bonus Question: Does a UPS need to match the PSU's watts? For instance, if I get a 450W PSU, does my UPS need to produce 450W too? Or will my UPS need to generate more watts because I'll have 2 monitors plugged into it as well?
I'm getting ready to build my first PC, so I'm trying to learn all that I can about this stuff. Thanks in advance!

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