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Series Resistor Calculator.

Calculate equivalent resistance of two series resistors.

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Equivalent resistance: 320 Ω

Equivalent resistance

320.000000Ω

Results update automatically as you type.

Use Cases

Designing simple voltage dividers

When you need to create a specific total resistance using two resistors in series, this calculator helps you quickly find the sum.

Example: R1 = 1 kΩ, R2 = 2 kΩ → total = 3 kΩ

Checking series circuit calculations

Verify your manual calculations for series circuits in electronics projects or homework.

Example: R1 = 470 Ω, R2 = 560 Ω → total = 1030 Ω

Frequently Asked Questions

How do I calculate the equivalent resistance of two series resistors?
Simply add the two resistance values together. For example, if R1 = 100 Ω and R2 = 220 Ω, the total resistance is 100 + 220 = 320 Ω. This calculator does that addition for you.
What is the unit of the result?
The result is in ohms (Ω), the same unit as the input resistances. Since the calculator adds the two values, the unit remains ohms.
Can I use this calculator for more than two resistors?
No, this calculator is designed for exactly two resistors. For more than two, you would add all resistance values together manually or use a calculator that supports multiple inputs.

Tips & Common Mistakes

Tips

  • Ensure both resistance values are in ohms (Ω). If you have values in kΩ or MΩ, convert them to ohms first (1 kΩ = 1000 Ω).
  • For series resistors, the total resistance is always greater than the largest individual resistance.
  • If you have more than two resistors, add them one pair at a time using this calculator, or sum all values manually.
  • Use the result to calculate current in a series circuit with Ohm's Law: I = V / R_total.

Common Mistakes to Avoid

  • Forgetting to convert units: mixing ohms and kilohms without conversion leads to incorrect results.
  • Using the formula for parallel resistors (product over sum) instead of simple addition.
  • Entering negative values or zero, which are not valid for resistance in typical circuits.

Last updated: August 13, 2026