The parallel resistor calculator is a tool for determining the equivalent resistance of a circuit with up to five resistors in parallel. Read on or jump to the series resistor calculator.

Resistors in parallel formula

A parallel circuit is characterized by a common potential difference (voltage) across the ends of all resistors. The equivalent resistance for this kind of circuit is calculated according to the following formula:

1/R = 1/R1 + 1/R2 +... + 1/Rn


  • R is the equivalent parallel resistance
  • R1, R2, ... Rn are the resistances of individual resistors numbered 1...n.

The units of all values are Ohms (symbol: Ω). 1 Ohm is defined as electrical resistance between two points that, when applied with a potential difference of 1 volt, produces a current of 1 ampere. Hence, 1Ω = 1V / 1A or, in SI base units, Ω = kg * m^2 / (s³ * A²).

How to calculate parallel resistance

  1. Establish the values of resistance for all resistors connected in parallel. For example, you can use three resistors of , and respectively.
  2. Input these values in our parallel resistor calculator.
  3. Read the result. In this example, 1/R = 1/4 + 1/3 +1/6, hence 1/R = 0.75 and R = 1.33 Ω. Notice that the equivalent resistance is lower than any of the individual values for resistors in parallel.

Other uses of the parallel resistor calculator

The principle is the same as when determining capacitance in series or induction in parallel - you can use it for these calculations, too. Just remember that units are not the same!

If you would like to find out the value of power dissipated in the resistor, try the Ohm's law calculator.

Bogna Haponiuk

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Parallel Resistor Calculator