What is Equivalent Resistance?

Equivalent resistance is the single resistance value that could replace an entire network of resistors while maintaining the same current flow and voltage drop across the connection points. In electrical engineering and physics, simplifying complex circuits into an equivalent resistance is a fundamental step in circuit analysis using Ohm's Law.

Series vs. Parallel Circuits

There are two primary ways resistors are connected:

• Series Connection: Resistors are connected end-to-end. The current has only one path to flow. The total resistance is the sum of all individual resistances.
• Parallel Connection: Resistors are connected across the same two nodes. The voltage across each resistor is the same. The reciprocal of the equivalent resistance is the sum of the reciprocals of each individual resistor.

How to Use This Calculator

1. Select whether your resistors are in Series or Parallel from the dropdown menu.
2. Choose your preferred unit (Ω, kΩ, or MΩ).
3. Enter the values for your resistors. You can add as many resistors as needed by clicking "Add Resistor".
4. Click "Calculate" to see the final equivalent resistance and the step-by-step breakdown of the formula used.

Formula for Calculation

For Series: Req = R1 + R2 + R3 + ...

For Parallel: 1/Req = 1/R1 + 1/R2 + 1/R3 + ...

Frequently Asked Questions

Why does parallel resistance decrease the total?

In a parallel circuit, adding more resistors provides more paths for the electric current to flow, which reduces the overall opposition (resistance) of the circuit.

Can I mix units?

This calculator assumes all inputs use the unit selected in the dropdown. If you have mixed units, please convert them to a single base unit (like Ohms) before inputting.