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Current Divider Calculator

Electronics & PhysicsResistors and Capacitors

Optional third parallel branch.

Optional fourth parallel branch.

Current through R1 —
Current through R2 (A)
—
Equivalent resistance (Ω)
—
Voltage across the branches (V)
—

A current divider splits a total current between parallel resistors in inverse proportion to their resistance: Ix = I × Req ÷ Rx. With 1 A feeding 10 Ω and 20 Ω in parallel, Req is 6.667 Ω, so the 10 Ω branch carries 0.6667 A and the 20 Ω branch carries 0.3333 A.

About this tool

Anyone sizing a shunt, checking an LED bank, or working a circuits homework problem needs to know how a known current shares out between parallel branches. Enter the current flowing into the node and two to four branch resistances. The calculator returns the current in every branch, the percentage of the total each one takes, the power each resistor dissipates, the equivalent resistance of the bank and the common voltage across it, with the arithmetic written out line by line. It treats every branch as an ideal fixed resistor: it does not model a source's internal resistance, temperature drift, or reactive parts such as capacitors and inductors at AC frequencies.

How to use it

  1. Enter the total current

    Type the current in amperes that enters the parallel network; 20 mA is 0.02 A.

  2. Fill in R1 and R2

    Give the resistance of each branch in ohms. Two branches are the minimum.

  3. Add R3 or R4 if present

    The extra fields are optional; empty ones are left out of the network.

  4. Read the branch table

    Each row lists a branch's current, its share of the total and the watts it dissipates.

Examples

1 A into 10 Ω and 20 Ω

Total current into the network
1
Resistance R1
10
Resistance R2
20

Result Current through R1: 0.6667
Current through R2 (A): 0.3333
Equivalent resistance (Ω): 6.6667
Voltage across the branches (V): 6.6667

  1. 1/Req = 1/10 + 1/20 → Req = 6.6667 Ω
  2. V = I × Req = 1 × 6.6667 = 6.6667 V
  3. I1 = 1 × 6.6667 ÷ 10 = 0.666667 A
  4. I2 = 1 × 6.6667 ÷ 20 = 0.333333 A

The smaller resistor takes two thirds of the current, because current splits in inverse proportion to resistance.

6 A into 2 Ω, 3 Ω and 6 Ω

Total current into the network
6
Resistance R1
2
Resistance R2
3
Resistance R3
6

Result Current through R1: 3
Current through R2 (A): 2
Equivalent resistance (Ω): 1
Voltage across the branches (V): 6

  1. 1/Req = 1/2 + 1/3 + 1/6 → Req = 1 Ω
  2. V = I × Req = 6 × 1 = 6 V
  3. I1 = 6 × 1 ÷ 2 = 3 A
  4. I2 = 6 × 1 ÷ 3 = 2 A
  5. I3 = 6 × 1 ÷ 6 = 1 A

The conductances add to exactly 1 siemens, so the 6 V across the network gives clean whole-amp branch currents.

20 mA into four 100 Ω resistors

Total current into the network
0.02
Resistance R1
100
Resistance R2
100
Resistance R3
100
Resistance R4
100

Result Current through R1: 0.005
Current through R2 (A): 0.005
Equivalent resistance (Ω): 25
Voltage across the branches (V): 0.5

  1. 1/Req = 1/100 + 1/100 + 1/100 + 1/100 → Req = 25 Ω
  2. V = I × Req = 0.02 × 25 = 0.5 V
  3. I1 = 0.02 × 25 ÷ 100 = 0.005 A
  4. I2 = 0.02 × 25 ÷ 100 = 0.005 A
  5. I3 = 0.02 × 25 ÷ 100 = 0.005 A
  6. I4 = 0.02 × 25 ÷ 100 = 0.005 A

Equal branches share the current equally: 5 mA each, with 0.5 V across the bank.

How it is calculated

1/Req = 1/R1 + 1/R2 + … ; V = I × Req ; Ix = I × Req ÷ Rx ; Px = Ix² × Rx

I
total current entering the parallel network, in amperes
Rx
resistance of branch x, in ohms
Req
equivalent resistance of all branches in parallel
Ix
current through branch x
Px
power dissipated in branch x, in watts

Every parallel branch sees the same voltage, and Kirchhoff's current law says the branch currents add back to the total. Combining the two with Ohm's law gives Ix = V ÷ Rx = I × Req ÷ Rx. For two branches this reduces to the familiar I1 = I × R2 ÷ (R1 + R2). The power column applies P = I²R to each branch.

When not to use it

  • Do not use it for capacitors or inductors at AC; those need impedances, not resistances.
  • It does not apply when a voltage source drives the branches directly with no defined total current.
  • Nonlinear parts such as diodes or lamps change resistance with current, so the split will be off.

Common mistakes

  • Entering milliamps as amps: 20 mA must be typed as 0.02.
  • Expecting the larger resistor to take more current; it takes less.
  • Mixing kilohms and ohms between branches without converting first.
  • Using the series voltage divider formula, which puts the other resistor in the denominator differently.

Frequently asked questions

Why does the smaller resistor carry more current?

All parallel branches share one voltage. By Ohm's law I = V ÷ R, so a branch with half the resistance draws twice the current. The current divider is the mirror image of the voltage divider, where the larger resistor takes the larger share.

What is the two-resistor shortcut?

For two branches, I1 = I × R2 ÷ (R1 + R2) and I2 = I × R1 ÷ (R1 + R2). Notice each branch current uses the opposite resistor in the numerator. With 1 A, 10 Ω and 20 Ω, I1 = 1 × 20 ÷ 30 = 0.6667 A.

How is the equivalent resistance found?

Add the conductances (1/R) of every branch and take the reciprocal. Four 100 Ω resistors give 4 × 0.01 = 0.04 S, so Req = 25 Ω. The equivalent resistance is always lower than the smallest branch.

Do the branch currents always add up to the total?

Yes. Kirchhoff's current law requires the currents leaving a node to equal the current entering it, so the shares in the table sum to 100 percent apart from display rounding.

How do I pick a shunt resistor for an ammeter?

Put the meter's internal resistance in R1 and a trial shunt in R2, then enter the full-scale current. Adjust R2 until the R1 current equals the meter's full-scale deflection current.

Can I work in milliamps and kilohms?

The ratios hold in any consistent units, so kilohms in every branch give the same currents. The voltage and power columns, however, assume amperes and ohms, so convert before reading those values.

Cite this tool

Using this tool in an assignment, article or report? Copy a citation, or a link for your website.

APA

Tools Directory Editorial Team. (2026, October 27). Current Divider Calculator. Tools Directory. Retrieved October 27, 2026, from https://tools.milunir.com/electronics-physics/resistors-and-capacitors/current-divider-calculator/

MLA

Tools Directory Editorial Team. “Current Divider Calculator.” Tools Directory, 27 Oct. 2026, https://tools.milunir.com/electronics-physics/resistors-and-capacitors/current-divider-calculator/. Accessed 27 Oct. 2026.

Chicago

Tools Directory Editorial Team. “Current Divider Calculator.” Tools Directory. Last modified October 27, 2026. Accessed October 27, 2026. https://tools.milunir.com/electronics-physics/resistors-and-capacitors/current-divider-calculator/.

Link<a href="https://tools.milunir.com/electronics-physics/resistors-and-capacitors/current-divider-calculator/">Current Divider Calculator – Tools Directory</a>