Electrical · Free Calculator
Series and Parallel Resistor Calculator
Find the total resistance of up to six resistors connected in series or in parallel. Leave unused boxes empty.
SeriesParallelUp to 6 resistorsΩ, kΩ, MΩ
Series total7.9 kΩ
Parallel total599.77 Ω
Resistors counted3
How this result was calculated
- Series: R = R1 + R2 + … = 7.9 kΩ
- Parallel: 1/R = 1/R1 + 1/R2 + … → R = 599.77 Ω
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Series and Parallel Formulas
Series: RT = R1 + R2 + R3 + …
Parallel: 1 ÷ RT = 1 ÷ R1 + 1 ÷ R2 + 1 ÷ R3 + …
Parallel: 1 ÷ RT = 1 ÷ R1 + 1 ÷ R2 + 1 ÷ R3 + …
Worked example
1 kΩ, 2.2 kΩ and 4.7 kΩ give 7.9 kΩ in series and 600 Ω in parallel.
Key insight: the parallel total is always smaller than the smallest resistor. Two equal resistors in parallel give exactly half the value.
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Frequently Asked Questions
How do I calculate two resistors in parallel?
R = (R1 × R2) ÷ (R1 + R2). For 100 Ω and 300 Ω that is 75 Ω.
Does current divide equally in parallel resistors?
Only if they are equal. More current flows through the smaller resistance.
How are power ratings shared?
In series the largest resistor dissipates most power; in parallel the smallest does. Check each one with P = I²R or V²/R.
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