Parallel ResistanceThis calculator requires the use of
Javascript enabled and capable browsers. Begin by entering the
resistance values into the resistance input box. Please be sure to click
on the "Enter Resistance" button after each entry followed by clicking
on the resistance entry box to prepare for the next resistor value
entry. There is no reasonable limitation as to the number of entries as
long as you follow each entry by clicking on the "Enter Resistance"
button and again on the entry box to allow for the next entry. After the
last resistance value has been entered, click on the "Calculate
Resistance" button for the returned parallel resistance value and the
number of resistor values entered. Parallel resistance is NOT the same
as averaging. It uses the formula RT = 1 / ((1 / R1) + (1 / R2) + (1 /
R3)). There are other formulae for doing the resistance of only 2
resistors but this works with an unlimited number of resistors,
including 2. In the formula given, RT is the total (parallel) resistance
of the circuit, R1 is the resistance value of the first resistor, R2 is
the resistance value of the second resistor, R3 is the resistance value
of the third resistor, and on until the last resistor. Please remember
that RT is with no exception, always smaller than the lowest value
resistor in parallel. Input value is assumed to be ohms and returns in
the same input value. See the information below the calculator for
explanation of the formula. To calculate series resistance, use our
Series Resistance Calculator.
An
example (and test) of the formula is to use three
resistors, 100 ohms, 200 ohms and 300 ohms, all in a
circuit in parallel. The total (parallel) resistance
would be 1 / (1/100 (.01) + 1/200 (.005) + 1/300
(.00333)) or about 54.555 ohms. Accuracy is good to the
capability of your browser, generally 18 characters in
the display window. NaN is an indication of an error in
data entry or calculation; do the process again paying
close attention to your data entry.

Version 2.2.1 
 