What is a current divider calculator?
In parallel circuits, the total current splits into multiple paths. How much current flows in each branch depends on the resistance of that branch compared to the others. A current divider calculator applies the current divider rule to quickly determine the current in each branch of a parallel network.
This is useful when:
- Checking current sharing between parallel resistors
- Estimating sensor or shunt currents in measurement circuits
- Designing bias networks and reference dividers
- Verifying whether any branch will exceed its power rating
The current divider rule
For two resistors R1 and R2 in parallel that share a total current IT, the branch currents are:
-
Branch 1:
I1 = IT × R2 / (R1 + R2) -
Branch 2:
I2 = IT × R1 / (R1 + R2)
Notice that the smaller resistance gets the larger share of the current, because it offers a lower opposition to the applied voltage.
General form for N branches
For more than two parallel branches, it is convenient to work with conductance (G = 1 / R). If the total current is IT and each branch has resistance Rk (conductance Gk), then:
Ik = IT × (Gk / ΣGi) = IT × ( (1 / Rk) / Σ(1 / Ri) )
The calculator uses this general expression so it can handle any number of parallel resistors or loads.
Current divider vs voltage divider
It is helpful to contrast the current divider with the more familiar voltage divider:
| Concept | Voltage divider | Current divider |
|---|---|---|
| Topology | Series resistors | Parallel resistors |
| Shared quantity | Same current through all resistors | Same voltage across all branches |
| Output quantity | Voltage across a resistor | Current through a resistor |
| Rule | Voltage is proportional to resistance | Current is proportional to conductance (1/R) |
Worked examples
Example 1 – two parallel resistors
- IT = 2 A
- R1 = 100 Ω
- R2 = 50 Ω
Total current splits as:
I1 = 2 A × 50 / (100 + 50) ≈ 0.67 A
I2 = 2 A × 100 / (100 + 50) ≈ 1.33 A
The lower resistance (50 Ω) carries twice as much current as the 100 Ω branch.
Example 2 – three parallel branches
- IT = 1 A
- R1 = 100 Ω
- R2 = 200 Ω
- R3 = 50 Ω
Compute conductances:
G1 = 1/100 = 0.01 S
G2 = 1/200 = 0.005 S
G3 = 1/50 = 0.02 S
ΣG = 0.035 S
Then branch currents are:
I1 = 1 A × 0.01 / 0.035 ≈ 0.286 AI2 = 1 A × 0.005 / 0.035 ≈ 0.143 AI3 = 1 A × 0.02 / 0.035 ≈ 0.571 A
Design tips when using current dividers
- Check power in each branch: Once you know the current, compute P = I²R to verify that no resistor exceeds its power rating.
- Avoid relying on matched components for safety: Small tolerance differences can change current sharing; add margin or use dedicated current-sharing networks for power applications.
- Consider temperature coefficients: As resistors heat up, their value changes, which can further shift the current split in high-power circuits.
- Use current dividers for sensing: Small-value shunt resistors can be used in one branch to measure current without disturbing the rest of the network too much.
This calculator helps you visualize current sharing in parallel networks so you can design safer, more reliable power stages, sensor circuits and bias networks in industrial and embedded systems.
