- Published 12 Jun 2025
- Last Modified 12 Jun 2025
- 3 min
Parallel and Series Resistance Calculator
Need to calculate the resistance value for parallel and series resistors? Our free and easy-to-use calculator takes out the hard work and gives you the answer you need in a few clicks.
Choose the connection type, enter how many resistors you have and the resistance value of each one, and click ‘calculate’ and the output resistance equivalent will appear.
Understanding Parallel and Series Resistors
Resistors are commonly connected in a circuit either in series or in parallel, and each method affects the total resistance differently. Read on to find out what each means and the formula used to calculate total resistance for each connection.
Parallel Resistors
When resistors are connected in parallel, they are arranged so that both ends of each resistor are connected to the same two points in a circuit. This means the voltage across each resistor is the same, but the current splits and flows through each path separately. Parallel setups are often used to reduce resistance or balance current across components and are used to distribute load in power supplies and audio systems. Check out the parallel resistor formula below:
Formula: 1/R=1/R1 +1/R2 +…+1/Rn
R = Equivalent parallel resistance
R1, R2 = resistances of individual resistors numbered to n
Series Resistors
In a series connection, resistors are placed one after the other along a single path, meaning the same current passes through each resistor. Because the current must flow through every resistor in line, their individual resistances add up, resulting in a higher total resistance. This type of setup is commonly used to increase resistance, limit current, or divide voltage across components. Series resistors are great at limiting current to protect LEDs and other components. The series resistor formula is outlined below:
**Formula: **R=R1 +R2 +...+Rn
R = Equivalent series resistance
R1, R2 = resistances of individual resistors numbered to n
