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Resistors can be joined end to end (in series) or side by side (in parallel). This calculator finds the equivalent resistance both ways for up to five resistors. Leave unused boxes at 0.
In series the same current flows through each resistor and the resistances add. In parallel each resistor has the same voltage and the total resistance falls, because the current has more paths.
| Resistor R1 | 100 Ω |
| Resistor R2 | 220 Ω |
| Resistor R3 | 330 Ω |
| Resistor R4 | 0 Ω |
| Resistor R5 | 0 Ω |
| Total in series (Ω) | 650 |
| Total in parallel (Ω) | 56.8966 |
| Resistors used | 3 |
In series they give 650 Ω; in parallel just 56.8966 Ω.
Try this example →| Resistor R1 | 10 Ω |
| Resistor R2 | 10 Ω |
| Resistor R3 | 0 Ω |
| Resistor R4 | 0 Ω |
| Resistor R5 | 0 Ω |
| Total in series (Ω) | 20 |
| Total in parallel (Ω) | 5 |
| Resistors used | 2 |
Series: 20 Ω. Parallel: 5 Ω, half of one resistor.
Try this example →Each appliance gets the full 230 V, can be switched on and off independently, and one failing doesn't cut the others off. In series, every device would share the voltage and all would go off together.
Add them: R = R₁ + R₂ + R₃ + …
Add the reciprocals and take the reciprocal: 1/R = 1/R₁ + 1/R₂ + …
Yes, always.
Half of one of them: two 10 Ω resistors give 5 Ω.