What is the current divider rule?

The current divider rule states that when total current enters two parallel resistors, each branch carries a fraction of that current inversely proportional to its resistance. A lower resistance attracts more current.

What formula does this calculator use?

I1 = I_total × R2 / (R1 + R2) and I2 = I_total × R1 / (R1 + R2). The numerator uses the opposite resistor because lower resistance draws more current.

Do the branch currents always add up to the total current?

Yes. I1 + I2 = I_total is always true for two parallel branches. You can verify this with the percentages shown — they always sum to 100%.

What if both resistors are equal?

Equal resistors split the current exactly in half. Each branch carries 50% of the total current.

Can I use this for more than two branches?

This tool covers two parallel branches. For three or more parallel resistors, calculate the total equivalent resistance (R_eq) first, then find each branch current using I_n = I_total × (R_eq / R_n).

Current Divider Calculator

Enter total current and two parallel resistance values to instantly calculate the current through each branch.

Circuit Inputs

Total Current (I_total)

Resistance 1 (R1) — Ω

Resistance 2 (R2) — Ω

Results

Enter values and click Calculate

Current Divider Rule — Formula Reference

Branch 1 Current

I₁ = I_total × R2 / (R1 + R2)

Branch 2 Current

I₂ = I_total × R1 / (R1 + R2)

Parallel Resistance

R_eq = (R1 × R2) / (R1 + R2)

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Summary

Enter total current and two parallel resistance values to instantly calculate the current through each branch.

How it works

Enter the total current flowing into the parallel network (in mA or A).
Enter the resistance of Branch 1 (R1) in ohms.
Enter the resistance of Branch 2 (R2) in ohms.
The calculator applies the current divider rule: I1 = I_total × R2 / (R1 + R2) and I2 = I_total × R1 / (R1 + R2).
Results show branch currents plus a percentage breakdown of how current is split.

Use cases

Design parallel resistor networks in analog circuits.
Verify current distribution in LED driver circuits.
Troubleshoot unequal current sharing in power supply branches.
Teach or study the current divider rule in electronics courses.
Check biasing currents in transistor base networks.
Validate SPICE simulation results for parallel branches.

Frequently Asked Questions

Last updated: 2026-09-22 · Reviewed by Nham Vu