Parallel Resistor Calculator
Calculate the equivalent resistance and per-resistor current share for two or more resistors wired in parallel.
Input
One value per line or comma-separated. Enter at least two resistors.
Output
| Metric | Value |
|---|---|
| No data yet | |
| Resistor | Value | Conductance (S) | Current Share |
|---|---|---|---|
| No data yet | |||
Guides
The Parallel Resistor Calculator finds the equivalent resistance of two or more resistors wired in parallel, plus how current splits across each branch.
The formula
For resistors in parallel, the reciprocal of the equivalent resistance is the sum of the reciprocals of each resistor:
1/R_eq = 1/R1 + 1/R2 + ... + 1/RnWorking in conductance (G = 1/R, measured in siemens) makes this simpler — conductances just add:
G_total = G1 + G2 + ... + Gn
R_eq = 1 / G_totalThe equivalent resistance of a parallel network is always smaller than the smallest individual resistor, since adding a path only gives current more ways to flow.
Current distribution
Every resistor in a parallel network sees the same voltage across it (that's the defining property of "parallel"). Since current = voltage × conductance, and voltage is shared, each resistor's share of the total current is proportional to its own conductance:
Current Share_i = G_i ÷ G_total × 100%The resistor with the lowest resistance carries the most current.
How to use it
- Enter two or more resistor values, one per line or comma-separated.
- Pick the unit — Ω, kΩ, or MΩ.
The calculator returns the equivalent resistance, total conductance, the smallest/largest resistor in the set, and a per-resistor breakdown of conductance and current share, plus a step-by-step derivation.
Example
Three resistors — 100 Ω, 220 Ω, and 330 Ω — wired in parallel:
G_total = 1/100 + 1/220 + 1/330 = 0.0175758 S
R_eq = 1 ÷ 0.0175758 S = 56.8966 ΩThe 100 Ω resistor, being the smallest, carries the largest share of current — about 56.9%.
Does the order of the resistors matter?
No — parallel resistance is commutative, so 100, 220, 330 gives the same result as 330, 100, 220. The order only affects which row is labeled R1, R2, R3, etc. in the output table.
What if all my resistors are equal?
For n equal resistors of value R, the equivalent resistance is simply R ÷ n, and current splits evenly (100% ÷ n each).
Privacy
All calculations run entirely in your browser. Your figures are never uploaded or stored.
Use it from code
From 3 credits per callREST API
curl -X POST https://api.iotools.cloud/v1/tool/parallel-resistor-calculator \
-H "Authorization: Bearer YOUR_API_KEY" \
-H "Content-Type: application/json" \
-d '{
"resistors": "100\n220\n330",
"unit": "ohm"
}'Swap in your own key from your account. The tool's fields are the body — no wrapper.
Ask an AI agent
Use the IOTools `parallel-resistor-calculator` tool (Parallel Resistor Calculator) on this input:
YOUR_INPUT_HEREPaste this at any agent connected to the IOTools MCP server, then add your input.