Resistors in parallel formula
A parallel circuit is characterized by a common potential difference (voltage) across the ends of all resistors. The equivalent resistance for this kind of circuit is calculated according to the following formula:
1/R = 1/R1 + 1/R2 +... + 1/Rn
Ris the equivalent parallel resistance
R1, R2, ... Rnare the resistances of individual resistors numbered
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,
1Ω = 1V / 1A or, in SI base units,
Ω = kg * m^2 / (s³ * A²).
How to calculate parallel resistance
- Establish the values of resistance for all resistors connected in parallel. For example, you can use three resistors of
- Input these values in our parallel resistor calculator.
- Read the result. In this example,
1/R = 1/4 + 1/3 +1/6, hence
1/R = 0.75and
R = 1.33 Ω.
Other uses of the parallel resistor calculator
The principle is the same as when determining capacitance in series or induction in parallel - you can use it for these calculations, too. Just remember that units are not the same!
If you would like to find out the value of power dissipated in the resistor, try the Ohm's law calculator.