# Power Ratings—Given a power value and nothing else, how can resistor values be calculated?

I am going through "Circuit Analysis for Dummies". On pg 18, it says, "If you calculate the power dissipated as 0.1 watts, then a 0.25-watt resistor can handle this amount of power. A 0.125-watt resistor should be able to handle that amount as well, but when it comes to power ratings, err on the larger side."

The only information they had provided prior to this are these two well-known equations, $$P=i^2*R$$ and $$p = v^2/R$$. Given P = 0.1, how do I get the resistance without the voltage or current? I've gone far back into the book to ascertain that I'm not really missing other values...

Now you'd work out the power dissipated in the resistor, perhaps using $$P=I^2 R$$. It comes to 0.04 W, so you'd be fine with a 0.125 W resistor!