Current Divider Calculator
Enter the total source current and the component values for each parallel branch. The calculator applies the current divider rule to find how much current flows through each branch, shows the equivalent parallel impedance, and breaks down each branch as a percentage of the total. Choose between resistive, inductive, or capacitive circuit types, and add up to four branches.
What is the current divider rule?
When two or more components are connected in parallel, they all share the same terminal voltage. Because of this, the total current from the source splits across each branch in inverse proportion to that branch's impedance. A smaller resistance (or lower reactance) presents less opposition, so it draws a larger share of the current. The current divider rule is the parallel-circuit counterpart of the voltage divider rule and is a direct consequence of Kirchhoff's current law (KCL): the sum of all branch currents equals the total current entering the node.
How to use this calculator
Select the circuit type (resistive, inductive, or capacitive), enter the total source current, choose how many parallel branches you need (2 to 4), then fill in the component values for each branch. For inductive and capacitive circuits, enter the AC supply frequency as well. Results update instantly and include the current through each branch, the percentage share of each branch, and the equivalent parallel impedance. The "Show your work" panel traces every step of the calculation with your exact numbers. Use the bars visual to compare branch currents at a glance.
The conductance method for N branches
For two resistors the simplified two-resistor formula (I1 = I x R2/(R1+R2)) is easy to apply. For three or more branches, the conductance method is cleaner and always correct: convert each resistance to its conductance (G = 1/R), add all conductances to get G_total, then each branch current is Ik = I x Gk / G_total. The equivalent parallel resistance is 1/G_total, which is always less than the smallest individual resistance. The same conductance approach applies to inductive dividers (replace R with L) and to capacitive dividers (replace R with 1/C, or equivalently use C directly as the admittance proxy).
Inductive and capacitive current dividers
In an AC circuit, inductors and capacitors oppose current through their reactance rather than their resistance. For parallel inductors, the branch with smaller inductance has lower inductive reactance (XL = 2*pi*f*L) and therefore carries more current, and the division ratio follows I1/I2 = L2/L1, identical in form to the resistor case. For parallel capacitors the opposite is true: larger capacitance means lower capacitive reactance (XC = 1/(2*pi*f*C)), so the branch with the larger capacitor draws more current, and I1/I2 = C1/C2. These relationships hold at any single frequency where the circuit is purely reactive.
Current divider rule - quick reference formulas
| Circuit type | Branch 1 current | Branch 2 current | Equivalent impedance |
|---|---|---|---|
| Resistive (DC/AC) | I1 = I x R2 / (R1 + R2) | I2 = I x R1 / (R1 + R2) | Req = R1*R2 / (R1 + R2) |
| Inductive (AC) | I1 = I x L2 / (L1 + L2) | I2 = I x L1 / (L1 + L2) | XL_eq = 2*pi*f*Leq |
| Capacitive (AC) | I1 = I x C1 / (C1 + C2) | I2 = I x C2 / (C1 + C2) | XC_eq = 1/(2*pi*f*Ceq) |
| N parallel resistors | Ik = I x Gk / G_total | Gk = 1/Rk | Req = 1 / G_total |
Formulas for 2-branch parallel circuits by component type. For N branches, replace the opposite component value with the conductance (1/R) or admittance form.
Frequently asked questions
What is the formula for a current divider with two resistors?
For two parallel resistors R1 and R2 with total current I, the current through each branch is: I1 = I x R2 / (R1 + R2) and I2 = I x R1 / (R1 + R2). Notice that I1 uses R2 (the other resistance) in the numerator. A smaller R1 gives a larger I1, which reflects the fact that less resistance allows more current.
How do I apply the current divider rule to more than two branches?
Use the conductance method. Convert each resistance to a conductance: Gk = 1/Rk. Sum all conductances: G_total = G1 + G2 + ... + Gn. Then each branch current is Ik = I_total x Gk / G_total. This works for any number of parallel branches and also generalises to inductive and capacitive circuits by substituting the appropriate admittance values.
How does a current divider differ from a voltage divider?
A voltage divider uses series components: the same current flows through all resistors and the voltage splits in proportion to resistance. A current divider uses parallel components: the same voltage appears across all branches and the current splits in inverse proportion to impedance. Voltage dividers are used to step down voltage; current dividers are used to split current between loads.
Why is the equivalent resistance always smaller than the smallest branch resistance?
Adding a parallel path gives the current an extra route, which always reduces the overall opposition. Mathematically, Req = 1/(G1+G2+...) and G_total is always larger than any individual Gk, so Req is always smaller than any individual Rk. Even adding a very large resistor in parallel will slightly reduce the equivalent resistance.
Does the current divider formula change with frequency for resistors?
No. For ideal resistors the impedance is purely resistive and does not change with frequency, so the current divider formula is the same for DC and any AC frequency. For inductors and capacitors the reactance is frequency-dependent, so the division ratio changes as frequency changes. This is why filters and tuned circuits use reactive elements rather than just resistors.
How do I find the voltage across a parallel network from the branch currents?
The voltage across any parallel branch is V = Ik x Rk (Ohm's law). Because all branches share the same terminal voltage, you can also compute V = I_total x Req where Req is the equivalent parallel resistance shown by this calculator. Checking that Ik x Rk is the same for every branch is a quick way to verify your calculation.