電流分配計算機

How to use this calculator

1. Enter the total current I entering the two parallel resistors.
2. Enter the two resistor values R1 and R2 in ohms.
3. Click Calculate for the current in each branch, plus the parallel resistance and node voltage.

Worked example

With I = 2 A, R1 = 100 Ω and R2 = 220 Ω: I₁ = 2 × 220 / 320 = 1.375 A and I₂ = 2 × 100 / 320 = 0.625 A — the two add back to 2 A.

The current divider formula

When a current I enters two resistors in parallel, it splits in inverse proportion to the resistances — more current flows through the smaller resistor: I₁ = I × R₂ / (R₁ + R₂) and I₂ = I × R₁ / (R₁ + R₂). The current through R₁ uses R₂ on top (and vice-versa) — the key difference from the voltage divider.

Why it works

Both resistors share the same voltage V. By Ohm's law I₁ = V/R₁ and I₂ = V/R₂, and V = I × R_parallel with R_parallel = R₁R₂/(R₁+R₂). The two branch currents always add back up to the total current.

常見問題

What is the current divider formula?

For two parallel resistors, I₁ = I × R₂ / (R₁ + R₂) and I₂ = I × R₁ / (R₁ + R₂).

Which resistor carries more current?

The smaller resistor. Current divides in inverse proportion to resistance, so the lower-resistance branch takes the larger share.

How is it different from a voltage divider?

In a current divider each branch current uses the opposite resistor on top; in a voltage divider the output uses its own resistor.