Parallel
Parallel Resistor Calculator
Use this parallel resistor calculator when two or more resistors share the same two nodes. Enter each branch value and the calculator finds equivalent resistance. Add an applied voltage when you also need total current and power.
- 1 / Rtotal = 1/R1 + 1/R2 + … + 1/Rn
- Gtotal = 1 / Rtotal
How It Works
- 1
Enter each branch resistor
Add every resistor that connects across the same two circuit nodes.
- 2
Keep mode set to parallel
The calculator starts in parallel mode for this page and applies the reciprocal-resistance rule.
- 3
Add voltage if needed
Optional voltage lets the calculator report total current and power for the equivalent branch.
Parallel resistor formula
For parallel resistors, conductance adds: 1 / R_total = 1 / R1 + 1 / R2 + ... + 1 / Rn. For two resistors, the shortcut is R_total = (R1 x R2) / (R1 + R2).
Worked example
- 1.Combine 10 kΩ and 15 kΩ in parallel.
- 2.Use R = (R1 x R2) / (R1 + R2).
- 3.R = (10,000 x 15,000) / (10,000 + 15,000) = 6,000 Ω.
The equivalent resistance is 6 kΩ. A parallel result is always lower than the smallest branch resistance unless a branch is open.
Common mistakes
Do not add parallel resistor values directly. Add reciprocal values, then take the reciprocal of the sum.
A 0 Ω branch shorts the entire parallel network to 0 Ω.
Power sharing is only even when branch resistances match closely.
This calculator handles one pure parallel group, not an arbitrary mixed series-parallel graph.
Parallel resistor FAQ
Why is parallel resistance lower than every branch?
Each added branch gives current another path. More paths increase conductance, and resistance is the reciprocal of conductance.
What is the formula for two parallel resistors?
For two resistors, use R_total = (R1 x R2) / (R1 + R2). For three or more, sum the reciprocals and take the reciprocal of that sum.
Can parallel resistors increase power rating?
Yes, but only when values and temperature behavior are close enough to share current evenly. For safety-critical or high-power circuits, choose a properly rated part.
Does order matter in a parallel network?
No. Parallel branches share the same two nodes, so the total is the same no matter how you list the resistors.
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