PROTESHEA / CIRCUIT TOOLS

Parallel resistor
calculator.

One voltage. Multiple paths.
Find the equivalent resistance, then see how the current splits.

01 Build your circuit

2 branches

Enter a value for each parallel branch. Mix units freely.

Up to 12 branches
Optional details

Adds current and power results.

Applied to every branch.

Try an example

Equivalent resistance

LIVE RESULT
500 Ω

Less than the smallest branch, as expected.

Total current—
Total power—

Add a supply voltage to calculate current and power.

Your parallel network

Same voltage across every branch

02 Follow the current

I = V / R · P = V² / R

Each branch sees the same supply voltage. Lower resistance carries more current.

Resistance, current, power and share of total current for each branch
BranchResistanceCurrentPowerCurrent share

THE MATH, MADE VISIBLE

Add the paths.
Lower the resistance.

Parallel branches give current more ways to flow. Add their conductances (1/R), then take the reciprocal to get the equivalent resistance.

Req = 1 / (1/R1 + 1/R2 + …)
01 / SANITY CHECK

Smaller than the smallest.

With two or more positive resistances, the equivalent resistance is always below the smallest branch.

02 / QUICK SHORTCUT

Equal resistors? Divide by the count.

For N identical resistors, Req = R / N. Two 1 kΩ resistors give 500 Ω.

03 / REAL COMPONENTS

Check the power rating.

Calculated power is ideal dissipation, not a recommended rating. Choose suitable headroom and follow the component’s temperature derating guidance.

Assumptions, units and edge cases

This calculator models ideal resistors in parallel with an ideal DC voltage source. It does not model source resistance, wiring, heating or AC reactance.

mΩ = 0.001 Ω · kΩ = 1,000 Ω · MΩ = 1,000,000 Ω. Use a decimal point or scientific notation (for example, 4.7 or 1e3). Each value must be non-negative and finite. Supported nonzero resistance: 10⁻¹² to 10¹⁵ Ω.

A 0 Ω branch shorts the network: equivalent resistance is 0 Ω, but ideal short-circuit current and power cannot be determined from this model. Real current depends on source and wiring impedance. Remove a branch to model an open circuit.

Tolerance bounds are the worst case when every resistor is simultaneously at its low or high tolerance limit. These are resistance bounds, not a statistical estimate. Current and power use nominal values.

Results are displayed to six significant figures. Educational estimates only; verify component ratings and real circuit conditions before building.