How to calculate PSU wattage requirements

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herr5407

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Hello all.

I've done a little searching on these forums and have found a few posts concerning what I need but the links don't work. (or else my laptop at work sucks. which it does)

Anyways, I was wondering if someone could explain to me the math I could do to determine wattage required for a PC. Can I take a figure off a part i install and then do some math to compare it to the PS wattage?

This may be the easiest thing ever I just remember reading some complicated thing somewhere. Can anyone explain?
 
I've seen the calculators before but I'm more interested in calculating the actual wattage myself on paper.

The journey systems calculator is very nice though. I was just wondering if there was a forumla to follow.
 
P = E * I
where
P is power in watts
E is volts
I is current in amps
 
Also found this, not sure if it's correct. A 30% buffer seems fairly large.

*Formula used = sum of wattage used by devices x 30% (or 1.3) buffer to be safe. And remember fans, cooling devices and anything connected via Firewire(IEEE 1394) or USB also draws power directly from the system.

Thanks!
 
the 30% is known as a power factor which equates to 1/1.30 or 76.9% loading
of the power supply. GOOD design says you never run anything at 100% of the
rating as that shortents the life of the component :(
 
Ok. I was planning on building a computer in the near future and I've heard of a few people cooking PSU's from overload so I thought I would be safe and calculate it myself to get the proper wattage.

Thanks for the information jobeard!
 
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