For all intents and purposes 1206 SMD resistors are all that’s needed for Arduino applications.
20mA to 100mA.
Anything smaller you need magnification.
@larryd I would not expect starter kits to contain SMD resistors!
@Travisbklein Ah, V^2/R, I get it now! But that's not the right way to calculate the resistor power needed. The formula is correct but the values are not. None of your resistors will have 12V across them, and none of them are 1K, are they? A more convenient formula to use is I^2R, for example if the current will be 20mA and the resistor is 220R, the power dissipation would be 0.020^2x220=0.088W, so 1/16W would be too small, 1/10W is borderline, but 1/8W is fine. When buying resistors as a beginner, choose 1/4W, they're easy to handle and enough for almost all beginner circuits.
I'm asking because I'm concerned the thin resistors that came in the starter pack which are 1/8w? 1/16w? are not enough.
They are 1/8W.
PaulRB:
@larryd I would not expect starter kits to contain SMD resistors!
Was thinking of the PDF I linked to in post #17 when I wrote that.
The OP would buy an assortment from a company like Jameco, Amazon etc.