Resistors in Parallel Calculator
Find the total resistance of parallel resistors.
Comma-separated, in ohms
Results update as you type.
How it works
When resistors are connected in parallel, current can flow through multiple paths at once, and this calculator finds their combined, or equivalent, resistance. You enter two or more resistance values, and it returns the total resistance of the parallel combination. The rule is that the reciprocal of the total equals the sum of the reciprocals of each resistor, so you add up one over each resistance and then take the reciprocal of that sum. A striking and useful property is that the equivalent resistance of a parallel combination is always less than the smallest resistor in the group, because adding more parallel paths gives the current additional routes, reducing overall opposition. For two equal resistors, the total is exactly half of one; for many resistors, it keeps dropping. This contrasts with series resistors, whose resistances simply add. Parallel configurations are everywhere in circuits: household wiring connects outlets in parallel so each gets the full voltage, and parallel resistors are used to achieve specific resistance values or to share current and power. Understanding parallel resistance is essential for circuit analysis and design. Enter your resistor values separated by commas to compute the total parallel resistance.
1 / R_total = 1/R₁ + 1/R₂ + …
For resistors in parallel, the reciprocal of the total resistance equals the sum of the reciprocals of each resistance. The total is then the reciprocal of that sum. The equivalent resistance is always smaller than the smallest individual resistor, because parallel paths give current more ways to flow.
Source:Electrical engineering
We review all our tools from time to time to ensure accuracy.
Worked example
How to use this calculator
- 1
Enter your values
Enter resistances.
- 2
Adjust the options
Fine-tune any options to match your situation.
- 3
Read your result
Total resistance updates instantly as you type — no button to press.
Frequently asked questions
How do you calculate parallel resistance?
Add the reciprocals of all the resistances, then take the reciprocal of the sum. For two 4-ohm resistors, one quarter plus one quarter is one half, so the total is 2 ohms. The calculator handles any number of resistors when you enter them separated by commas.
Why is parallel resistance always smaller?
Connecting resistors in parallel gives current more paths to flow through, which reduces the overall opposition. So the equivalent resistance is always less than the smallest individual resistor. Adding another parallel resistor, no matter how large, only lowers the total further, since it provides an additional route for current.
What is the difference between series and parallel?
In series, resistors are connected end to end so current flows through each in turn, and their resistances add. In parallel, resistors share the same two nodes so current splits among them, and the reciprocals add. Series raises total resistance, while parallel lowers it below the smallest resistor.
What happens with two equal resistors in parallel?
Two equal resistors in parallel give a total resistance of exactly half the value of one. Three equal resistors give one third, and so on: n equal resistors in parallel give one nth of a single value. This is a handy shortcut for equal resistors without applying the full reciprocal formula.
Where are parallel resistors used?
Parallel connections appear throughout electronics and wiring. Household outlets are wired in parallel so each receives the full supply voltage independently. Designers use parallel resistors to obtain non-standard resistance values, to share current and dissipate power across multiple components, and to provide redundancy. Analyzing them is a core skill in circuit design.