Current Divider Calculator
Calculate current distribution through two, three, or four parallel resistive branches.
About the current divider rule
A current divider calculator determines how a known total current separates among parallel branches. Every branch connected across the same two nodes has the same voltage, but a lower resistance carries more current. The calculator converts each entered resistance to conductance, adds those conductances, and assigns each branch the fraction represented by its conductance. For branch i, the relationship is Ii = Itotal × (1/Ri) / Σ(1/R). This conductance form works cleanly for two, three, or four branches and avoids repeatedly finding equivalent resistances. For two resistors, the familiar shortcut says that current through one resistor equals total current multiplied by the opposite resistance divided by the sum of both resistances. That apparently reversed relationship is simply another form of the conductance equation. A 100-ohm branch in parallel with a 200-ohm branch therefore carries twice as much current. When all branch resistances are equal, current divides equally. The calculated branch currents always sum to the entered source current, apart from small display-rounding differences. Use resistance values that represent the complete resistance of each parallel path, including any series elements within that path. All resistance inputs may use ohms because only their ratios determine the split. The total current is entered in amperes, and every result is also shown in amperes. Empty third and fourth branches are ignored, making the same form useful for common two-resistor networks and larger parallel arrangements. The ideal current-divider rule assumes steady conditions, linear resistors, and branches connected to the same pair of nodes. It does not model reactive impedance, changing temperature, component tolerance, source limits, or transient behavior. For alternating-current circuits containing capacitors or inductors, complex impedance and phase must replace ordinary resistance. Treat these results as design and study estimates, then confirm practical circuits against component ratings and measurements. Positive branch resistance is required because a zero-ohm ideal branch creates a short circuit for which the ordinary finite-resistance division formula is not applicable.
Current divider examples
These examples show how conductance controls the current split.
| Inputs | Output | Explanation |
|---|---|---|
| 10 A; 100 Ω, 100 Ω | 5 A, 5 A | Equal resistances share current equally. |
| 12 A; 10 Ω, 20 Ω, 20 Ω | 6 A, 3 A, 3 A | The 10-ohm branch has twice the conductance. |
| 8 A; 30 Ω, 60 Ω | 5.333 A, 2.667 A | The lower resistance carries two-thirds of the total. |
How to calculate branch current
- Enter the total current supplied to the parallel network.
- Enter positive resistance values for at least two branches.
- Leave unused third or fourth resistance fields empty.
- Select Calculate and review each branch current.
- Check that the displayed branch currents add to the total current.
Frequently asked questions
Why does the lower resistance receive more current?
Parallel branches share one voltage, so Ohm's law gives more current to a branch with less resistance. Current is proportional to conductance, which is the reciprocal of resistance.
Do the branch currents add to the total current?
Yes, conservation of charge requires their sum to equal the source current. Tiny differences can appear when displayed values are rounded.
Can I enter resistance in kilohms?
Yes, if every branch uses the same resistance unit, the ratios and current split are unchanged. The labels use ohms for clarity, so convert mixed units before entering them.
What happens when all resistances are equal?
The total current divides equally among all active branches. Four identical branches each receive one quarter of the total.
Can this calculator analyze AC circuits?
It directly analyzes purely resistive branches under steady conditions. Reactive AC branches require complex impedance and phase-aware calculations instead.