# How to Calculate the Total Resistance With a Calculator

Written by william garmany
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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:
Moderate

### Things you need

• Scientific calculator

## 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:

"1/((1/20)+(1/30)+(1/40))"

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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