Current Divider Calculator

Enter the total input current and two parallel resistor values to see how the current splits between them, plus the equivalent resistance and voltage across the pair.

Quick Facts

Current divider rule
I1 = Itotal x R2/(R1+R2)
Each branch's share uses the OTHER resistor in the numerator — the opposite of a voltage divider.
Equivalent resistance
Req = (R1 x R2)/(R1+R2)
Two resistors in parallel always have a lower resistance than either one alone.
Smaller resistor wins
Current favors the path of least resistance
Because parallel branches share the same voltage, the lower-resistance branch carries more current.

Your Results

Calculated
Current Through R1
-
I1 = Itotal x R2/(R1+R2)
Current Through R2
-
I2 = Itotal x R1/(R1+R2)
Equivalent Resistance
-
Req = (R1 x R2)/(R1+R2)
Voltage Across the Pair
-
V = Itotal x Req

Ready

Enter the total current and two resistor values, then press Calculate.

How to Use the Current Divider Calculator

A current divider is two (or more) resistors wired in parallel so that a single incoming current splits between them. Because the branches share the same two nodes, they share the same voltage — and Ohm's law then dictates how the total current divides: the branch with less resistance carries a larger share of the current. This calculator takes a total input current and two resistor values and returns how much current flows through each resistor, the parallel (equivalent) resistance of the pair, and the voltage that appears across them.

Deriving the current divider formula

Start from the fact that R1 and R2 are in parallel, so the voltage across each is identical: V = I1R1 = I2R2. The two branch currents must also add up to the total current entering the node: Itotal = I1 + I2. Substituting I2 = I1R1/R2 into that sum and solving for I1 gives the current divider rule:

  • I1 = Itotal × R2 / (R1 + R2) — current through R1
  • I2 = Itotal × R1 / (R1 + R2) — current through R2
  • Req = (R1 × R2) / (R1 + R2) — the single resistor that would draw the same total current at the same voltage
  • V = Itotal × Req — the voltage that appears across both resistors

Notice each branch formula puts the other resistor on top. That is the signature of a current divider and the reason the smaller resistor always ends up with the larger current — it is the mirror image of the voltage divider formula, which puts the same resistor on top.

Practical notes and common uses

  • Shunt (ammeter) resistors: a low-value shunt is placed in parallel with a meter movement so most of the current bypasses the meter, letting a small-range meter read a much larger current.
  • Sharing load current: paralleling power resistors, MOSFETs, or LEDs divides current between them, but only evenly if their resistances (or on-resistances) are closely matched — mismatched parts will run hot unequally.
  • Sensor and bias networks: current-divider reasoning shows up wherever a fixed current source feeds two parallel paths, such as current-mode biasing in analog circuits.
  • General case (more than two resistors): convert each resistance to conductance (G = 1/R) and use Ik = Itotal × Gk / (G1 + G2 + … + Gn); the two-resistor formula above is the special case of this rule.

Frequently Asked Questions

What is the current divider formula for two resistors?
For two resistors R1 and R2 in parallel sharing a total input current Itotal, the current through each branch is I1 = Itotal × R2/(R1+R2) and I2 = Itotal × R1/(R1+R2). Each branch's share uses the OTHER resistor in the numerator, and I1 + I2 always equals Itotal.
Why does more current flow through the smaller resistor?
Both resistors share the same voltage because they are in parallel (V = I1R1 = I2R2). Since voltage is fixed, Ohm's law (I = V/R) means the branch with less resistance must carry more current — current takes the path of least resistance.
How is a current divider different from a voltage divider?
A voltage divider uses resistors in series to split a voltage, and the output fraction uses the SAME resistor in the numerator (Vout = Vin × R2/(R1+R2)). A current divider uses resistors in parallel to split a current, and the formula uses the OPPOSITE resistor in the numerator, which is why the smaller resistor gets the larger current share.
Can the current divider rule handle more than two resistors?
Yes. For any number of parallel branches, convert each resistance to conductance (G = 1/R) and use Ik = Itotal × Gk / (G1+G2+...+Gn). The two-resistor formula above is just the simplified version of this general rule.

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