Calculate series and parallel resistance
Enter the values of the resistors and choose how they are connected. The calculator finds the total resistance and shows the working.
No connection. Your numbers have been kept. Please try again.
No connection. Your numbers have been kept. Please try again.
The connection determines how the resistors add up
In a series connection, the resistors are placed one after the other. In a parallel connection, they are spread over branches between the same two points. The same set of resistors therefore gives different results depending on the connection.
Enter the values in Ω separated by semicolons or spaces. Then choose series or parallel. The calculator finds the total resistance for the chosen connection.
Formulas for series and parallel
In series the values are added: R = R₁ + R₂ + …. The result gets larger when a positive resistance is added to the series.
In parallel, R = 1 / (1/R₁ + 1/R₂ + …) is used. First the reciprocal of each resistance is found, then they are added, and finally the reciprocal of the sum is taken. For positive resistances, the result is smaller than the smallest single resistance.
Examples of both connections
10 Ω, 20 Ω and 30 Ω in series give 10 + 20 + 30 = 60 Ω.
For two 10 Ω resistors in parallel, the working is 1 / (1/10 + 1/10) = 1 / (0.1 + 0.1) = 1 / 0.2 = 5 Ω.