Calculates total resistance for series and parallel connection of up to 3 resistors
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Resistor calculator for series and parallel connection
Resistors must be combined for complex circuits. Our calculator determines the total resistance for:
- Series circuit: R_ges = R1 + R2 + R3 (resistors add up)
- Parallel connection: 1/R_ges = 1/R1 + 1/R2 + 1/R3
- LED series resistors: Several LEDs in series or parallel
- Voltage divider: Generate partial voltages for sensors
- Measuring bridges: Dimensioning Wheatstone bridges
Row connection: Resistors are simply added together. 3× 100Ω in series = 300Ω. The current is the same everywhere, voltages add up.
Parallel circuit: Total resistance is less than the smallest individual resistance. 2× 100Ω in parallel = 50Ω. Voltages are equal, currents add up.
Special case 2 equal resistors in parallel: R_ges = R / 2. Three equal resistors: R_ges = R / 3.
Practical tip: By combining the E12 standard series (10, 12, 15, 18, 22, 27, 33, 39, 47, 56, 68, 82 Ω), you can generate almost any required resistor value. Example: 22Ω + 33Ω = 55Ω (series). 100Ω || 100Ω = 50Ω (parallel).
Series and parallel resistors: examples
Series: R = R1 + R2. Parallel: 1/R = 1/R1 + 1/R2 – the total is always smaller than the smallest single resistor. Two equal resistors in parallel give exactly half.
| Resistors | In series | In parallel |
|---|---|---|
| 100 Ω and 100 Ω | 200 Ω | 50 Ω |
| 100 Ω and 220 Ω | 320 Ω | 68.8 Ω |
| 220 Ω and 330 Ω | 550 Ω | 132 Ω |
| 1 kΩ and 1 kΩ | 2 kΩ | 500 Ω |
| 1 kΩ and 2.2 kΩ | 3.2 kΩ | 687.5 Ω |
| 4.7 kΩ and 10 kΩ | 14.7 kΩ | 3.2 kΩ |
| 10 kΩ and 10 kΩ | 20 kΩ | 5 kΩ |
| 10 kΩ and 22 kΩ | 32 kΩ | 6.88 kΩ |
