Series Resistor Calculator

By Bogna Szyk and Álvaro Díez
Last updated: Sep 20, 2021

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

Resistors in series formula

A series circuit is characterized by a common current that flows through all of the resistors - there is only one path the current can follow. The equivalent resistance for this kind of circuit is a sum of all individual resistances:

R = R₁ + R₂ +... + Rn

where:

  • R is the equivalent series 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, 1 Ω = 1 V / 1 A or, in SI base units, Ω = kg·m²/(s³·A²).

The formula for calculating equivalent resistance in a series circuit is similar to that for equivalent inductance in a series circuit.

How to calculate series resistance

  1. Establish the values of resistance for all resistors connected in series. For example, you can use three resistors of 4 Ω, 3 Ω, and 6 Ω, respectively.
  2. Input these values in our series resistor calculator.
  3. Read the result. In this example, R = 4 + 3 + 6, hence R = 13 Ω. Notice that the equivalent resistance is higher than any of the individual values for resistors in series.

Other uses of the series resistor calculator

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

If you would like to find out the value of power dissipated in the resistor, try the power dissipation calculator. You can also check out our wheatstone bridge calculator to learn how to measure unknown resistance.

Bogna Szyk and Álvaro Díez
drawing of resistors in series in an electrical circuit
Mode
Calculate equivalent resistance
Resistor 1 (R₁)
Ω
Resistor 2 (R₂)
Ω
You can add up to 10 resistors, fields will appear as you need them.
Results
Input at least one resistor to obtain a result.
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