Series Resistor Calculator Explained

By Last updated: June 07, 2023

Series Resistor Calculator

Series resistor formula

The formula to calculate the equivalent resistance of resistors connected in series is R = R1 + R2 + ... + Rn.

Series resistors circuit
$${R} = {R_1} + {R_2} + ... + {R_n}$$

Where R is the equivalent or total resistance value of the series circuit and R1, R2, ...Rn is the resistance value of each resistor.

How to calculate series resistor

When you connect resistors in series, each resistor shares the same current with a different voltage. Depending on each resistor's resistance value, the voltage between the individual resistor can be found using Ohm's law formula.

${V_1}={R_1} \times {I}, {V_2}={R_2} \times {I}, ... , {V_n}={R_n} \times {I}$

So the total voltage between the power source is the sum of all voltages combined.

${V}={R_1} \times {I}+{R_2} \times {I}+ … +{R_n} \times {I}$
${V}={I} \times ({R_1}+{R_2}+ … +{R_n})$

Alternatively, we can calculate the total voltage using the equivalent resistance connected to the power source.

${V} = {I} \times {R}$

We can now find the equivalent resistance using the following formula.

${I} \times {R} = {I} \times ({R_1}+{R_2}+ … +{R_n})$
${R} = {R_1} + {R_2} + ... + {R_n}$

Example: Calculating equivalent resistance of a series circuit

What is the total resistance of a connection consisting of three resistors: ${R_1} = {8.00 Ω}, {R_2} = {12.00 Ω},$ and ${R_3} = {21.00 Ω}$?

To find an equivalent resistance of the series resistors in the connection, use the following formula and follows by entering the given values.

${R} = {R_1} + {R_2} + {R_3}$
${R} = {8.00\ Ω} + {12.00\ Ω} + {21.00\ Ω}$


${R} = {41\ Ω}$

The total resistance of the current connection with three resistors is ${R} = {41\ Ω}$.

How to use the calculator

Our parallel resistor calculator calculates the equivalent resistance in real-time as you enter or change each resistor's value. It is responsive and works on either desktop or mobile.

The calculator starts with two input boxes for two resistors, and you can add as many as you like by using the Add Resistor button.

You can also change the individual resistance unit from Ω (ohms) to  (milli-ohms),  (kilo-ohms), and  (mega-ohms) by using the drop-down menu next to each box.

The result will appear in two places. The Result section will show only the final value of the equivalent resistance of the parallel circuit, while the Calculation section will show you the detailed steps.

Steps to use Series Resistor Calculator
Using the calculator to find the result
Series Resistor Calculator

Series Resistor Calculator App

About this app

Easily calculate the equivalent resistance value of multiple resistors connected in series with our calculator. We will also show you the formula and how to solve the problem.

App availability

You can use the calculator for free as a PWA web app online or install it locally on any modern operating system, including Android, iOS, Windows 11/10, and macOS.

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