Series Resistance Calculator

Resistors in series

When you connect resistors in series, the total resistance goes up. The current has to pass through each resistor in turn, meeting each one's resistance along the way, so the total is simply the sum of them all.

The formula

The total resistance R_total of resistors in series is the sum of the individual values:

R_total = R₁ + R₂ + R₃ + ··· + R_n

Example

Take three resistors in series of 100 Ω, 200 Ω and 300 Ω. Add them together:

Picture them connected end to end. The current flows through the first, then the second, and so on, with each one adding its resistance to the total.

Two things to keep in mind

• The total is always larger than any single resistor in the chain.
• The current is the same through every resistor, but the voltage across each one depends on its resistance, a bigger resistor drops more voltage.

Putting resistors in series is the straightforward way to reach a value you don't have on hand by combining ones you do.