Current Divider Calculator — Parallel Resistor Current Split
Enter the total supply current and two parallel resistors to calculate the current through each branch, the equivalent parallel resistance and the common voltage across the combination.
mA
Ω
Ω
I₁ = I × R₂ / (R₁ + R₂) — the branch with lower resistance carries more current
- 1
Sum of resistances
1,000 + 2,000 = 3,000 - 2
Current through R₁
10 × 2,000 ÷ 3,000 = 6.667R₂ appears in the numerator — the branch with lower resistance carries more current.
How does this calculator work?
In a two-branch parallel circuit, current splits inversely to resistance: I₁ = I × R₂/(R₁+R₂) and I₂ = I × R₁/(R₁+R₂). Enter total current and both resistances to get each branch current, the equivalent parallel resistance R_p = R₁R₂/(R₁+R₂), and the common voltage V = I × R_p.
Formula
How this is calculated
When two resistors R₁ and R₂ are wired in parallel, the voltage across them is identical. By Ohm's law, the current through each branch is inversely proportional to its resistance — the branch with the lower resistance carries more current. The current-divider rule captures this: I₁ = I × R₂/(R₁+R₂). Counterintuitively, the formula for I₁ has R₂ (the other resistor) in the numerator, not R₁ — the larger the other branch's resistance, the larger the fraction routed through branch 1.
The equivalent parallel resistance R_p = R₁R₂/(R₁+R₂) is always less than either individual resistor. The voltage across the combination is V = I × R_p (Ohm's law on the equivalent circuit), and I₁ + I₂ = I exactly, confirming Kirchhoff's current law. This calculator presents current in milliamps and derives the voltage in volts, suitable for typical electronics design scenarios.
For n resistors in parallel, the general rule is I_k = I × G_k / G_total, where G_k = 1/R_k is the conductance of branch k and G_total = Σ G_k. Current divides in proportion to conductance, not resistance.
Frequently asked questions
Both branches see the same voltage. By Ohm's law I = V/R, so a lower R gives a higher I at the same V. The current-divider formula I₁ = I × R₂/(R₁+R₂) captures this: when R₁ ≪ R₂, R₂/(R₁+R₂) → 1 and almost all the current flows through branch 1.
For the parallel resistance and voltage it does not — R_p and V are symmetric. For the individual currents the labelling matters: I₁ always refers to the branch with resistance R₁. Swapping the labels swaps the calculated I₁ and I₂ values.
Compute the total conductance G_total = 1/R₁ + 1/R₂ + 1/R₃ + …. The current through branch k is I_k = I × (1/R_k) / G_total. The equivalent resistance is R_p = 1/G_total, which is always less than the smallest individual resistor.
TG we-Calculate Editorial Team. (2026). Current Divider Calculator — Parallel Resistor Current Split [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/current-divider-calculator
TG we-Calculate Editorial Team. "Current Divider Calculator — Parallel Resistor Current Split." TG we-Calculate. 2026. https://we-calculate.com/calculator/current-divider-calculator.
TG we-Calculate Editorial Team, "Current Divider Calculator — Parallel Resistor Current Split," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/current-divider-calculator
@misc{wecalculate_current_divider_calculator, title = {Current Divider Calculator — Parallel Resistor Current Split}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/current-divider-calculator}}, year = {2026}, note = {TG we-Calculate} }
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