220 Ω and 330 Ω
- Input
- par 220 330
- Expected output
- 132
220 × 330 ÷ 550 = 132 Ω.
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parallel resistor calculator
Connecting resistors in parallel is the way to get a value smaller than any of them, or to split power between parts. The calculation, though, is not a sum: you add the inverses. The tool opens with 1 kΩ, 2.2 kΩ and 4.7 kΩ in parallel and shows the equivalent, the series total for comparison and, optionally, the current and power of each branch for a given voltage.
220 × 330 ÷ 550 = 132 Ω.
Equal ones: half the value.
Total conductance of 1.667 mS.
100 ÷ 4 = 25 Ω.
47 ÷ 2 = 23.5 Ω.
1,000 ÷ 3 ≈ 333.3 Ω.
Add the inverses and invert the result: R = 1 ÷ (1 ÷ R1 + 1 ÷ R2 + ...). For two, R = R1 × R2 ÷ (R1 + R2). Example: 220 Ω and 330 Ω give 132 Ω. The result is always smaller than the smallest resistor.
1 ÷ R = 1 ÷ R1 + 1 ÷ R2 + ... For two, R = R1 × R2 ÷ (R1 + R2). For N equal ones, R = R1 ÷ N.
Each added resistor opens another path for the current, and more paths conduct more. Total conductance is the sum of conductances, always above the largest, which leaves the resistance below the smallest.
Add the three inverses and invert the total. With 1 kΩ, 2.2 kΩ and 4.7 kΩ: 1/1000 + 1/2200 + 1/4700 = 0.001667 S, and the inverse is 599.8 Ω. The tool accepts up to 20 values.
Each branch takes V ÷ R. The smallest value takes the largest current. At 12 V, 1 kΩ takes 12 mA and 4.7 kΩ takes 2.55 mA. The sum of the branches is the source current.
The math runs in your browser; no value is sent to a server. Combinations use nominal values: resistor tolerance adds on top of the error shown.