Parallel Circuit Voltage Calculator

Use this tool to calculate the equivalent impedance of any number of resistors in parallel, the voltage drop across each and the total current.

There are two configurations considered in this post.

Voltage Calculator in a Parallel Circuit

Parallel Resistance Formula

The total effective resistance is given by the formula:

Rtotal = (1/R1 + 1/R2 + 1/R3 +…. + 1/Rn)-1

The voltage across each resistor is the same

V = V1 = V2 = … = Vn

The total current is given by:

I = V/Rtotal

Using Ohm’s Law, the current through each resistor is inversely proportional to the value of the resistance. It is given by the formula

I1=V1/R1

The total current is the sum of the currents through each resistor

I = I1 + I2 + I3 … + In

Voltage Calculator in a Parallel Circuit with Series Resistor

This tool calculates the voltage across a parallel configuration of resistors when there’s an additional resistor or resistors in series.

Series and Parallel Resistance Formula

Rparallel = (1/R1 + 1/R2 + 1/R3 +…. + 1/Rn)-1

Rseries = R1 + R2 + R3 +…. + Rn

Rtotal = Rparallel + Rseries

Vparallel = (Rparallel/(Rparallel + Rseries))*V

Example Calculation

Consider three resistors in parallel: 1 Ω, 3 Ω, and 5 Ω and two resistors in series 1 Ω and 2 Ω

The total parallel resistance Rparallel = 0.652 Ω

The total series resistance Rseries = 3 Ω

If V = 5V,

Vparallel = 5*(0.652/3.652) = 0.89V

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