How to determine PSU watt req. For system!!!

[Sujeet]

I have seen many people posting threads for psu for specific rigs and receiving decent and satisfactory ans from TDF guys but how actually is the power req. calculated for system!!!
I mean i have seen several online psu watt calculators from different psu manufacturers but are they of any good and if yes how accurate they are and how to use them to get idea about power req. of pc.!
1.Thermaltake Power Supply Calculator
2.eXtreme Power Supply Calculator

 

[whitestar_999]

i think both are based on same source though extreme seems to be the original one.select capacitor aging as 25% & the value it will give should be more than enough.

 

[d6bmg]

The second link is good.
BTW, for which config you do want a new PSU? Please mention it.

 

[Sujeet]

no i dont need a new psu ...just got one recently ...its just for knowledge..!!