Resistor R1:
Resistor R2:
Equivalent Resistance (Req):
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Using the Equivalent Resistance Calculator
Series Equivalent Resistance Calculator
To use the series resistance calculator, set the Series/Parallel option to “Series.” Then, under Value to Calculate select the value you wish to calculate. Next, enter the known values (R1, R2, or Req). Finally, press Calculate.
For example, you set R1 to 10k ohms and R2 to 1.2k ohms. When you click Calculate, the equivalent resistance of the series combination will appear in the Req box.
Calculating Series Equivalent Resistance
To calculate the equivalent series resistance of n resistors, simply add up the resistance of each resistor. Equation 1 shows the standard series resistance equation, which is used by the calculator above.
Parallel Equivalent Resistance Calculator
To use the parallel resistance calculator, set the Series/Parallel option to “Parallel.” Then, under Value to Calculate select the value you wish to calculate. Finally, press Calculate to initiate the calculation.
For example, you can enter 11k ohms into the Req field and 22k ohms into the R1 field. Set the Value to Calculate field to R2, then press Calculate. The result is 22k ohms for R2, revealing that you will need two 22k ohm resistors in parallel to make 11k ohms.
Calculating Parallel Equivalent Resistance
To calculate the equivalent parallel resistance of n resistors, use the standard parallel resistance equation:
To calculate the equivalent parallel resistance of two resistors, the equation simplifies to:
For calculating R1 or R2, the following equation is used. Assume R1 is the one you want to calculate (the equation is the same for R2):
Rules for Resistor Values
Input the value of the resistor in the corresponding input field. Choose the resistance unit using the dropdown menu to the right of each input field. The following unit suffixes are available:
- k = kilo = x 1000
- M = Mega = x 1000000
Meet the Author:
Hi, I’m Dominic. By day, I’m an engineer. By night, I repair and modify guitar effects! Since 2017, I’ve been independently modifying and repairing guitar effects and audio equipment under Mimmotronics Effects in Western New York. After coming out with a series of guitar effects development boards, I decided the next step is to support that community through content on what I’ve learned through the years. Writing about electronics gives me great joy, particularly because I love seeing what others do with the knowledge they gain about guitar effects and audio circuits. Feel free to reach out using the contact form!