Current Divider Calculator
Enter total current and both branch resistances to get each branch's current — remembering the 'opposite resistor' formula that trips everyone once.
Last updated: 2026-09-28
How the calculation works
- Both branches share the same voltage; currents split inversely to resistance.
- The formula carries the OPPOSITE branch's resistance in the numerator — the classic first-time error.
- The percentage share shows dominance: the 100 Ω branch takes more than the 220 Ω branch.
Formula
I₁ = I_total × R₂ / (R₁ + R₂) I₂ = I_total − I₁
| Symbol | Meaning | Unit |
|---|---|---|
I₁, I₂ | Branch currents | A |
R_eq | Equivalent parallel resistance | Ω |
Worked example
Interpreting the result
The current divider is how shunts, current mirrors and parallel loads all work: lower resistance grabs more current. It is also the warning behind paralleling unequal loads — the lowest-value path hogs current and its share of heating. For more than two branches, compute R_eq first and use I_branch = I_total × (R_eq/R_branch).
Assumptions
- Two parallel branches sharing one voltage node pair.
- DC or purely resistive AC.
Limitations
- More than two branches needs the equivalent-resistance form.
- Reactive branches split current by impedance magnitude and phase — AC adds vector math.
Frequently asked questions
What is the current divider formula?
I₁ = I_total × R₂ ÷ (R₁ + R₂) for two branches — notice the OPPOSITE resistor in the numerator. The smaller resistance draws the larger current.
Why does the formula use the opposite resistor?
Because branches share the same voltage: I = V/R, and V = I_total × R_eq. Working it through, each branch's current ends up proportional to the OTHER branch's resistance.