PS Calculators?

[Saber]

Anybody know of a freeware reliable, trustworthy PS calculator online? Is it true that if your unknowingly operating below your PCs needed voltage things can appear to be working fine as you secretly damage your PC? If anybody knows a good manual calculation freehand that has worked for them please share? Goal: to match best PS w/o going overboard and not under board either? Enlighten! I'm googling and tried several, but not sure the programs are tilted towards getting you to purchase their product, kinda like on line registery checkers do?

[Spock]

I haven't been posting much lately. Were you ever able to find any reliable information?