Current Divider Calculator
How a current splits between two or three resistors in parallel, with the equivalent resistance and the voltage across them.
Results
Current in branch 1
0.6875
A
Current in branch 2
0.3125
A
Current in branch 3
0.0000
A
Equivalent parallel resistance
68.750
Ω
Voltage across the branches
68.750
V
What this tool does
In parallel, the current takes every path at once, and each branch carries a share proportional to its conductance, one over its resistance: the smaller resistor takes the bigger share, the opposite of a voltage divider. With two branches the rule shortens to I₁ = I × R₂ ÷ (R₁ + R₂), which is easy to get backwards. It is how an ammeter shunt works, and why LEDs should not share one resistor in parallel: tiny differences between them make one take most of the current. Leave branch 3 at 0 if there are only two.
Formula
Iₖ = I × (1/Rₖ) ÷ (1/R₁ + 1/R₂ + 1/R₃)
Variables
| Symbol | Meaning | Unit |
|---|---|---|
it | Total current into the branches | A |
r1 | Resistance of branch 1 | Ω |
r2 | Resistance of branch 2 | Ω |
r3 | Resistance of branch 3 (0 = none) | Ω |
I1 | Current in branch 1 | A |
I2 | Current in branch 2 | A |
I3 | Current in branch 3 | A |
RP | Equivalent parallel resistance | Ω |
V | Voltage across the branches | V |
Worked example
- Total current into the branches1 A
- Resistance of branch 1100 Ω
- Resistance of branch 2220 Ω
- Resistance of branch 3 (0 = none)0 Ω
- Current in branch 10.6875 A
- Current in branch 20.3125 A
- Current in branch 30.0000 A
- Equivalent parallel resistance68.750 Ω
- Voltage across the branches68.750 V
Limitations
- The formula assumes ideal conditions: no friction losses, no air resistance and no efficiency losses unless you enter them.