Parallel Resistor Calculator
Add each resistor to the list, flip between series and parallel, and read the total resistance as you type, scaled to ohms, kilohms or megohms.
This parallel resistor calculator adds up any number of resistors and shows the combined value the moment you edit a row. Switch the toggle to work as a series parallel resistance tool: series adds the values, parallel drops the total below the smallest resistor. As a resistor combination calculator it takes 2, 3 or a dozen values, and as a total resistance calculator it auto-scales the answer to Ω, kΩ or MΩ. Everything runs in your browser with nothing uploaded.
Resistors
Total resistance (series)
650 Ω
3 resistors added together
- Resistors
- 3
- Sum of values
- 650 Ω
In series the values simply add up, so the total is always larger than any single resistor. In parallel the total drops below the smallest resistor, and equal values split evenly, so two equal resistors in parallel give half their value.
Real resistors carry a tolerance (often 1% or 5%), so the built circuit lands near this figure rather than exactly on it. Standard E-series values rarely hit an arbitrary target, so combine common values to get close.
How it works
- 1
Pick series or parallel
Choose how the resistors are wired. Series stacks them end to end; parallel connects them across the same two nodes.
- 2
Enter each resistor
Type a value in ohms for every resistor, adding or removing rows so the list matches your circuit.
- 3
Read the total
The combined resistance updates live, with the resistor count, the sum of the values and, for parallel, the equivalent conductance.
Instant & 100% private — nothing is uploaded
Every calculation runs locally in your browser. The income, balances and goals you enter stay on your own device and are never sent to a server — nothing is stored, logged or shared.
Frequently asked questions
- How do I calculate two resistors in parallel?
- Take the reciprocal of each value, add them, then take the reciprocal of that sum: 1 / (1/R1 + 1/R2). Two 100 Ω resistors give 1 / (0.01 + 0.01) = 50 Ω. The calculator does this for as many resistors as you add.
- What is the total of resistors in series?
- Series resistance is just the sum of the values, so 100 + 220 + 330 comes to 650 Ω. Because you only ever add, the series total is always larger than the biggest single resistor in the chain.
- Why is a parallel total smaller than the smallest resistor?
- Each parallel path gives the current another route, so the combination passes more current than any single resistor would, which means less resistance. The result always lands below your smallest value, and equal resistors in parallel split evenly.
- Can I combine more than two or three resistors?
- Yes. Use the add button to grow the list to as many rows as your circuit has, and the trash icon to drop one. The math holds for any count, so a resistor combination calculator with ten values works the same as with two.
- What is the equivalent conductance shown for parallel?
- Conductance is the reciprocal of resistance, measured in siemens. In parallel the conductances add directly, which is why the tool shows it in millisiemens next to the total, an easier number to add in your head than the reciprocals.
- How do I hit an exact target resistance?
- Standard E-series resistors rarely land on an arbitrary value, so combine common ones: two in series to raise the total, or two in parallel to lower it. Tweak the rows here until the total sits close enough for your tolerance.
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