Resistors in Series Calculator
Find the total resistance of series resistors.
Comma-separated, in ohms
Results update as you type.
How it works
When resistors are connected end to end in a single path, they are in series, and this calculator finds their total resistance by adding them. You enter two or more resistance values, and it returns the sum, which is the equivalent resistance of the series combination. The rule could not be simpler: series resistances add directly, because the same current must flow through each resistor one after another, and each contributes its full opposition to that current. As a result, the total resistance of a series chain is always greater than any individual resistor, and adding more resistors in series always increases the total. This is the opposite of parallel resistors, whose combined resistance is less than the smallest. Series connections are common in circuits: components like resistors, switches, and fuses are placed in series so the same current passes through all of them, and series resistors are used to limit current, drop voltage, and build voltage dividers. The voltage divides across series resistors in proportion to their resistances, while the current stays the same throughout. Understanding series resistance is a foundation of circuit analysis. Enter your resistor values separated by commas to compute the total series resistance.
R_total = R₁ + R₂ + R₃ + …
For resistors in series, the total resistance is simply the sum of all the individual resistances. Because the same current flows through each resistor in turn, their opposition to current adds directly. The equivalent resistance is always larger than any single resistor in the series chain.
Source:Electrical engineering
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Worked example
How to use this calculator
- 1
Enter your values
Enter resistances.
- 2
Adjust the options
Fine-tune any options to match your situation.
- 3
Read your result
Total resistance updates instantly as you type — no button to press.
Frequently asked questions
How do you calculate series resistance?
Add up all of the individual resistances one by one. For resistors of 4, 4, and 2 ohms connected in series, the total is 10 ohms. The calculator sums any number of resistors you enter separated by commas. Series resistance is the simplest combination, since the values add directly together.
Why do series resistances add?
In a series circuit, the same current flows through every resistor in turn, so each resistor's opposition to that current adds to the total. There is only one path, and the current must pass through each component fully. This makes the total resistance the straightforward sum of all the individual resistances.
Is series resistance larger or smaller than the individual resistors?
Series resistance is always larger than any single resistor in the chain, because each added resistor increases the total opposition to current. This is the opposite of parallel resistors, where the combined resistance is smaller than the smallest one. Adding resistors in series always raises the total resistance.
How does voltage behave across series resistors?
The current is the same through all series resistors, but the voltage divides among them in proportion to their resistances, a larger resistor dropping more voltage. The sum of the voltage drops equals the total supply voltage. This is the basis of the voltage divider, a common use of series resistors.
Where are series resistors used?
Series connections appear when the same current must flow through several components, such as a fuse or switch in line with a load, or a current-limiting resistor before an LED. Series resistors also form voltage dividers to produce reference voltages. Understanding them is fundamental to analyzing and designing electronic circuits.