Circuit Analysis calculator
Series Circuit Calculator
Use this resistive series loop calculator when each resistor is in one current path and the inputs are source voltage plus resistor values. The tool adds the resistor string, solves loop current with Ohm’s Law, reports resistor voltage drops and power, and can work backward from a target current in design mode. For a broader DC or RLC operating-point check, use the Circuit Analysis Calculator.
Updated July 10, 2026
Enter source voltage and each resistor in the resistive series loop before using the result. This tool adds the resistor string, solves loop current, and then reports voltage drops and power for the entered values.
Series method: add the resistor string, divide source voltage by total resistance, then use the loop current for each voltage-drop and power result.
Enter source voltage and up to five resistor values to solve current, voltage drops, and power
Calculator Inputs
Calculation Results
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Calculation history
Example Calculations
More examples. Open to review 1 additional calculation example.
How to Use
How to use the series circuit calculator
- Select the calculation mode: voltage and current, total resistance, power analysis, or circuit design.
- Enter at least two resistor values. The calculator supports up to five resistors in the series string.
- When the selected mode uses a source, enter the source voltage.
- For design mode, enter the desired current so the calculator can determine the required total resistance.
- Review total resistance, loop current, voltage drops, and power results that apply to the chosen mode.
Formula quick reference
| Quantity | Formula | Meaning |
|---|---|---|
| Total resistance | Rtotal = R₁ + R₂ + ... + Rn | All resistors add in a series string |
| Loop current | I = V / Rtotal | The same current flows through every resistor |
| Voltage drop | Vᵢ = I × Rᵢ | Each resistor drops voltage in proportion to its resistance |
| Power in a resistor | Pᵢ = I² × Rᵢ | Use to compare against resistor wattage ratings |
| Voltage check | ΣVᵢ = Vsource | The sum of voltage drops should match the source voltage |
This calculator is limited to ideal resistive series networks. It does not model capacitors, inductors, complex impedance, or time-dependent transients. For those cases, use the related tools below.
If you need a parallel branch comparison, use the Parallel Circuit Calculator. For dedicated divider work, see the Voltage Divider Calculator. For quick V-I-R checks, use the Ohm’s Law Calculator.
After the Series Circuit Result
Once the loop current and resistor drops are known, carry the result into the next workflow step instead of stopping at the loop math.
- Series Circuit Voltage & Current Worksheet to record source voltage, total resistance, loop current, voltage drops, power, and measurement notes.
- Series-Parallel Resistance Chart to compare equivalent resistance before branch and divider checks.
- Parallel Circuit Calculator when the next question is branch current and equivalent resistance in a parallel network.
- Circuit Analysis Calculator when the circuit is no longer a purely resistive series string and needs a one-source DC or RLC operating-point check.
- Voltage Divider Calculator when the series chain is being used as a divider reference.
Common Applications
More applications. Open to review 2 additional use cases.
Frequently Asked Questions
Why is the current the same through every resistor in a series circuit?
A series circuit has only one current path, so the same current must flow through each element in the loop. What changes from resistor to resistor is the voltage drop, not the current.
Does this calculator work for AC circuits?
It works for ideal resistive circuits where the impedance is purely resistive and steady-state Ohm’s Law applies. It does not model reactance, phase angle, or transient behavior from capacitors or inductors.
What does design mode tell me?
Design mode calculates the total resistance needed to reach the target current from the entered source voltage. It then compares that target against the resistance already entered and shows whether you need to add or remove resistance.
When should I use the parallel circuit calculator instead?
Use the parallel calculator whenever the components sit on separate branches and each branch sees the same source voltage. In a series circuit there is one current path and the voltage divides among the resistors.
Related Calculators
Parallel Circuit Calculator
Solve equivalent resistance, branch current, total current, conductance, and resistive power for parallel branches.
Circuit Analysis Calculator
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Voltage Divider Calculator
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Series Resistor Calculator
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Ohm's Law Calculator
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Power Calculator
Solve DC, single-phase AC, and balanced three-phase power relationships from voltage, current, power factor, and power values.