Physics Formulas

Formula for Finding Resistance

Below is a formula for finding resistance often used in physics. We will also discuss Ohm's Laws. Before we discuss the formula for finding resistance, let's define what resistance is.

What is resistance in physics?

Resistance is defined by the resistance formula:

Formula for Finding Resistance


  • R = resistance (Ohm)
  • V = potential difference (V)
  • I = current (A)

Note that:

  • 1 kilohm is 10 3 ohms
  • 1 megohm = 10 6 ohms
What is Ohm's Law?

Ohm's Law for a metallic conductor is that the current is proportional to the applied potential difference for constant physical conditions. It follows that the resistance of an ohmic conductor is constant and does not change when the current changes.

The above equation for resistance (formula for finding resistance) is not an expression of Ohm's Law but the equation used to define resistance. The above formula for finding resistance does not express the fact that V/I = R is independent of I for an ohmic conductor.