How to Calculate the Total Resistance With a Calculator

Written by william garmany
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How to Calculate the Total Resistance With a Calculator
Scientific calculators provide you with many more options than standard calculators. (Jupiterimages/BananaStock/Getty Images)

Calculating the total resistance in a circuit can be a challenge; fortunately, with scientific calculators you can solve total resistance easily. The easier of the two kinds of resistance -- resistors in series -- comprises simply adding the total of all the resistors; this can be done with any calculator. When it comes to resistors in parallel, a scientific calculator is required to utilise all of the functions you will need to solve the problem.

Skill level:

Things you need

  • Scientific calculator

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    Resistors in Series

  1. 1

    Find the resistance of each of the resistors.

  2. 2

    Add the value of each resistor using the calculator. For example, If you have three resistors with respective resistances of 20, 30 and 40 ohms, simply add: 20 + 30 + 40.

  3. 3

    Press the "=" key on the calculator to sum the quantities and get your total. In the example provided, you will have a total of 90 ohms in this resistor series.

    Resistors in Parallel

  1. 1

    Find the resistance of each of the resistors in parallel in the circuit.

  2. 2

    Enter the computation into your calculator using the following formula:

    Total resistance = 1/ ((1/resistor 1) + (1/resistor 2) + (1/resistor 3)...(1/resistor x))

    where x = the total number of resistors.

    Using the same numbers as the previous example, for three resistors with resistances of 20, 30 and 40 ohms respectively, enter into your calculator:


    to solve the formula.

  3. 3

    Press "=" on your calculator to get the total resistance. In this example, you should have a total resistance of 9.23 ohms.

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