Use the parallel resistor calculator to solve equivalent resistance, branch current sharing, and optional power breakdown for two or more resistors in parallel.
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Parallel resistor calculator Add two or more resistors to find the equivalent parallel resistance. Enter a supply voltage to see branch current and power breakdowns.
Resistor rows
Each row contributes conductance to the shared parallel network.
Common parallel resistor examples
Resistor 1
Resistor 2
Network note
The equivalent resistance always comes from the combined conductance of the valid resistor rows. A supply voltage only adds branch current and power calculations.
Add at least two resistors Enter two or more positive resistor values to solve the parallel network.
Parallel resistor calculator: equivalent resistance, branch current, and power
A parallel resistor calculator solves more than the reciprocal formula. This page also explains the main assumptions behind the parallel resistor calculator result, highlights the supporting figures shown by the calculator, and helps the reader use the estimate without overstating what a quick online tool can prove.
What this parallel resistor calculator covers
This page accepts two or more resistor values, converts mixed input units into ohms, and solves the equivalent resistance by summing branch conductance.
An optional supply voltage adds branch-by-branch current and power so you can see how the load splits across the network instead of stopping at the equivalent resistance alone.
The live result also surfaces branch share and open-branch sensitivity, which makes the page more useful for current-divider planning, fault intuition, and checking whether one low-value resistor dominates the network.
Parallel networks add conductance, not resistance
In a parallel network each branch provides another path for current, so the total conductance increases as more valid branches are added. Equivalent resistance is then the reciprocal of that total conductance.
That is why the equivalent resistance of a true parallel network always comes out lower than the smallest branch resistance. Adding another parallel branch cannot make the network look more resistive unless the branch is effectively open and contributes no conductance at all.
This conductance-first view is often easier to reason with than repeatedly inverting resistor values, especially when several branches are present or when you want to compare how much each branch contributes to the total.
Gtotal = 1/R1 + 1/R2 + ... + 1/Rn
Each resistor contributes conductance to the shared network.
Req = 1 / Gtotal
Equivalent resistance is the reciprocal of the combined conductance.
Every branch sees the same voltage
Once a supply voltage is entered, each resistor branch uses that same branch voltage to determine its current and power. Lower-resistance branches therefore draw more current and dissipate more power.
The branch table is useful when you need to spot a hot branch, verify current sharing, or confirm whether one resistor dominates the load. If one resistor is much smaller than the others, it can account for a large share of total conductance and therefore a large share of the current as well.
That is why a parallel resistor calculator becomes much more practical when it reports current-share percentages rather than only branch current values. The percentages make it obvious which branch is carrying the circuit.
Ibranch = V / Rbranch
Branch current follows directly from the shared branch voltage and the resistor value.
Pbranch = V × Ibranch = V² / Rbranch
Branch power rises as branch resistance falls when branch voltage stays fixed.
Itotal = I1 + I2 + ... + In
Total current is the sum of branch currents in the parallel network.
Worked example: 1 kΩ in parallel with 2 kΩ on a 9 V source
A classic worked example is 1 kΩ in parallel with 2 kΩ at 9 V. The conductance sum is 1/1000 + 1/2000, which gives 0.0015 S, so the equivalent resistance is about 666.7 Ω.
With 9 V across both branches, the 1 kΩ branch carries 9 mA and the 2 kΩ branch carries 4.5 mA. Total current is therefore 13.5 mA. The lower-value branch carries twice the current because it has twice the conductance.
This is a good reminder that current sharing in a resistor-only parallel network follows resistance inversely. A branch with lower resistance has a larger conductance share, larger current share, and larger power share.
What happens if the branches are identical
Identical parallel branches create a simple shortcut: equivalent resistance equals one branch value divided by the number of branches. Two identical 1 kΩ resistors in parallel give 500 Ω. Three identical 10 kΩ resistors in parallel give about 3.33 kΩ.
This shortcut is useful because many quick design checks involve repeated resistor values rather than arbitrary unmatched branches. It also gives you a fast sanity check when the calculator result seems surprising.
What happens if one branch opens
A useful practical question is what happens if one branch is removed or opens. In an ideal resistor-only parallel network, removing a branch reduces total conductance, so equivalent resistance rises. The total current drawn from a fixed-voltage source also falls.
The size of the change depends on which branch is removed. Opening a high-resistance branch may barely move the network because it contributed little conductance in the first place. Opening the lowest-value branch often causes the largest jump in equivalent resistance because that branch was carrying the largest share of the load.
Why one very small resistor dominates the network
If one resistor is much smaller than all the others, the equivalent resistance approaches that smallest branch. The higher-value branches still add conductance, but their effect may be modest compared with the dominant low-resistance path.
That matters because people often expect every added branch to matter equally. In reality, a 470 Ω branch in parallel with 1 kΩ and 2.2 kΩ will dominate both current and power at the same voltage source. This is one of the most important interpretation cues a parallel resistance calculator should make obvious.
What this calculator does not model
This calculator assumes ideal resistors in a simple DC-style parallel network. It does not model temperature rise, tolerance stacking, inductance, wiring resistance, or any reactive behaviour.
Use it as a planning and educational reference. If the network includes capacitors, inductors, time-varying sources, or thermal constraints, switch to the calculator that models those effects explicitly.
It also does not replace resistor wattage checks, measurement, or code- or product-level engineering review. The current and power numbers are only as good as the assumption that the source holds the entered voltage at the network terminals.
Frequently asked questions
Why is the equivalent resistance lower than the smallest resistor?
Because adding a parallel branch creates another current path, which increases total conductance. The reciprocal of that larger conductance is a smaller equivalent resistance. That is a defining property of a true parallel resistor network.
Do all parallel branches really see the same voltage?
Yes in the ideal model. Parallel branches connect across the same two nodes, so each branch sees the same node-to-node voltage. That is why branch current depends only on the resistor value when the branch voltage is fixed.
Can I mix ohms, kilohms, and megohms?
Yes. This calculator normalizes the entered branch values into ohms before it sums conductance and solves the equivalent resistance. Mixing units is fine as long as each entered value is positive and valid.
Does each branch draw the same current?
No. In an ideal parallel network the voltage is the same across every branch, so the current in each branch depends on that branch's resistance. Lower-resistance branches draw more current than higher-resistance branches.
What happens if one resistor is much smaller than the others?
The smallest resistor can dominate the network because it draws a disproportionate share of current and pulls the equivalent resistance downward. That is one reason branch-by-branch current checking is useful.
How do you calculate resistors in parallel?
For resistor branches in parallel, add conductance rather than resistance: 1/Req = 1/R1 + 1/R2 + ... + 1/Rn. A calculator typically converts each value into ohms first, sums the conductance, and then inverts that total to get the equivalent resistance.
What is the shortcut for two resistors in parallel?
For exactly two resistors, a common shortcut is Req = (R1 × R2) / (R1 + R2). That shortcut is mathematically equivalent to the reciprocal formula, but the conductance method scales more cleanly once you have three or more branches.
How do identical resistors behave in parallel?
Identical parallel branches divide the branch value by the number of branches. Two identical resistors halve the value, three divide it by three, and so on. The current also splits evenly because the branch resistances are the same.
What happens if one branch opens in a parallel circuit?
Equivalent resistance rises because the circuit loses one conductance path. The amount of change depends on how much conductance that branch contributed. If the opened branch had a high resistance, the change may be small. If it had the lowest resistance, the change is usually much larger.
Can I use this calculator for current divider problems?
Yes for resistor-only branch sharing at a known voltage. Once you enter supply voltage, the branch table shows the current in each branch, which is exactly the practical information most current-divider checks are trying to find.
Does adding another resistor in parallel always reduce total resistance?
Yes, as long as the added branch has a finite positive resistance and is actually connected in parallel. Every added branch increases total conductance, which means the equivalent resistance must fall.
Can this calculator replace power-rating checks?
No. It helps estimate branch current and power, but you still need to compare those results with actual resistor wattage ratings, voltage limits, thermal conditions, and the real behaviour of the circuit.
