Best Answer: Common unit: Ohm (ω) To find the SI unit, first take the definition of resistance, the Ohm's law: 1 ω = 1 V / 1 A, or shortly, ω = V/A. Now the ampere is itself a SI unit, volt is not. It's similarly easy and worth memorizing that J = VAs and J = kg*m^2/s^2. (I personally like to use the Joule as a side step.) Compare these two to get V = kg*m^2/(A*s^3). Plug in the ω above to get ω = kg * m^2 / (A^2 * s^3). Hope this helps!