How do you figure out required wattage in a pc setup?

[Cakesok]

Is there any simpler way to figure out the required wattage for a pc besides whipping out a calculator and researching all the numbers yourself?

 

[anxiousinfusion]

Even though you say voltage, I imagine you're looking for something like this: http://www.extreme.outervision.com/psucalculatorlite.jsp

 

[Cakesok]

Best answer selected by Cakesok.