What is the simplest way to calculate how much a resistor will heat up?
E.g. 1w, 2w tells us the power dissipation, but whether that means 1 degrees C above ambient or 20 on the body of the resistor, depends surely on the area of the resistor itself.
If there's an online calculator that does this - all the better, as I'm not one with Math (one mistake was that I didn't understand it as something practical at school - which it is, because it allows us to make practical things). But, if there's a simple formula, that should work too (you shouldn't need to be proficient to use formulas, as long as you can read them and/or put them into a program or a calculator).
There's no specific reason (e.g. ensuring that the heat caused by resistors in circuit will not affect other elements), as likely this only needs to be calculated for high quality PCB design and such, none of which I'm doing.
I'm just curious about roughly how hot a resistor will get at certain wattage.