Parallel Resistor Calculator
Calculate total resistance for resistors connected in parallel. Add as many resistors as you need — the circuit is illustrated automatically.
Up to 8 resistors.
How to use the calculator
- Enter your resistors in ohms, one per row.
- Add more resistors with "+ Add resistor" — the circuit diagram updates automatically with one branch per resistor.
- The calculator shows the total resistance and how many resistors are in use.
How a parallel connection is calculated
With a parallel connection, the resistors sit side by side between the same two points, so current can spread across several paths at once. Total resistance is found by adding the inverse values (1/R) and then flipping the result back:
Worked example: the same 10 Ω and 20 Ω resistors in parallel give 1 ÷ (1/10 + 1/20) = 6.67 Ω. Note that the total is lower than the smaller of the two — in series those same resistors would give 30 Ω, nearly five times as much.
The result is always lower than the lowest single resistor in the combination — because current gets more paths to flow through, it becomes overall easier for it to flow.
Why parallel connection always lowers resistance
In a parallel connection the current has several paths to choose between, so the total resistance is always lower than the smallest individual resistor. It seems backwards the first time you see it, but the water analogy fits: open an extra tap and more flows overall, however narrow the new tap is. Each new branch adds a route, never an obstacle.
Two equal resistors in parallel give exactly half the value, and n equal resistors give the value divided by n. In return, every branch has the full voltage across it — it is the current that divides, not the voltage. That is why the sockets in a house are wired in parallel: every appliance gets the same voltage, and switching one off does not affect the others.
Frequently asked questions
Why is total resistance lower with a parallel connection?
With a parallel connection, current gets several paths to flow through at the same time, making it overall easier for current to flow. That's why total resistance is always lower than the lowest single resistor in the combination.
How many resistors can I add?
The calculator supports up to 8 resistors in parallel. The principle is the same no matter how many: you add the inverse values (1/R) and then flip the result back.
What are parallel connections used for in practice?
Parallel connections are typically used in household wiring, so that each circuit gets the full supply voltage and works independently of the others — if one resistor or load fails, the rest of the circuit is unaffected.