Parallel Resistance Calculator

Calculate the total resistance in ohms of resistors that are in parallel by entering the value of each below.

Parallel Resistance:

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How to Calculate Resistors in Parallel

A resistor is a device that adds resistance to an electrical circuit. Resistance is measured in ohms (Ω), and that’s also the measure used by this calculator.

When resistors are added in parallel in a circuit, they are connected to the same points as each other, thus there are multiple paths that voltage can take. Because of this, the reciprocal of each resistance value must be added together to find the total resistance of the circuit.

Parallel Resistor Formula

When multiple resistors are added to a circuit in parallel the total resistance can be found using this formula.

1 / RT = 1 / R1 + 1 / R2 + 1 / R3 + … + 1 / Rn

Thus, the reciprocal of the total resistance of resistors connected in parallel is the sum of the reciprocal of each resistance.

electrical circuit diagram showing resistors connected in parallel
Diagram showing a circuit with 3 resistors connected in parallel.

For example, let’s find the total resistance of a circuit with 200 ohm, 400 ohm, and 500 ohm resistors connected in parallel.

1 / RT = 1 / 200 Ω + 1 / 400 Ω + 1 / 500 Ω
1 / RT = 0.005 + 0.0025 + 0.002
1 / RT = 0.0095
RT = 1 ÷ 0.0095
RT = 105.263 Ω