Parallel Resistor Calculator
Fast, accurate, and free online Parallel Resistor Calculator tool that runs directly in your browser.
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| # | R | Unit | |
|---|---|---|---|
| 1 | |||
| 2 |
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Other tools you may find usefulParallel resistor calculator - calculate equivalent resistance
Calculate equivalent resistance for any number of resistors connected in parallel. The calculator will immediately give you a result in ohms (Ω), and will also show the current and voltage in the circuit if you enter additional data. The perfect tool for electronics engineers, students and engineers designing electrical systems.
Run the parallel resistor calculator See formulas and examples
What is parallel connection of resistors
In a parallel connection, each resistor is connected directly to the same points in the circuit - this means that the voltage on each of them is the same, while the current is distributed proportionally to their resistance.
Equivalent resistance formula
1 / Rz = 1 / R₁ + 1 / R₂ + 1 / R₃ + ... + 1 / RₙTo calculate the equivalent resistance, simply reverse the sum of the reciprocals of all resistances. The result will always be smaller than the smallest resistor in the system.
Simplified formulas
For two resistors:
Rz = (R₁ × R₂) / (R₁ + R₂)
For three:
Rz = 1 / (1/R₁ + 1/R₂ + 1/R₃)The calculator supports any number of resistors - just enter their values and the result will be displayed immediately.
How to use the calculator
- Enter the resistor values in ohms (Ω), separated by commas.
- If desired, enter the supply voltage to calculate the total current.
- ClickCalculate- you will receive the equivalent resistance value and current parameters.
- You can also convert the units to kΩ or MΩ.
Calculation examples
Two resistors
R₁ = 100 Ω, R₂ = 200 Ω
Rz = (100×200)/(100+200) = 66.67 Ω
Three resistors
R₁ = 50 Ω, R₂ = 100 Ω, R₃ = 150 Ω
Rz = 1 / (1/50 + 1/100 + 1/150) = 27.27 Ω
Five 1 kΩ resistors
Rz = 1 / (5 × 1/1000) = 200 Ω
Example with voltage
R₁ = 1 kΩ, R₂ = 2 kΩ, U = 12 V
Rz = 666.7 Ω, I = 12 / 666.7 = 0.018 A
Comparison of parallel and series connection
| Feature | Parallel | Series |
|---|---|---|
| Formula | 1/Rz = Σ(1/R) | Rz = ΣR |
| Voltage | Constant for all resistors | Different for each |
| Current | Splits | Same throughout the circuit |
| Resultant resistance | Always less than the smallest R | Always greater than the largest R |
Ohm's law in calculations
U = I × Rz
I = U / Rz
P = U × IThanks to these relationships, the calculator can calculate not only the resistance, but also the current and power in the entire circuit.
Frequently asked questions (FAQ)
Does the voltage drop in a parallel connection?
No, the voltage across each resistor is identical - only the current changes.
Why is the parallel resistance lower?
Because current has many flow paths - each additional resistor reduces the total resistance of the circuit.
How to add resistors with different units?
All values should be given in ohms (Ω). The calculator automatically converts kΩ and MΩ.
Can different types of resistors be combined?
Yes, the parallel connection works regardless of the tolerances and power of the components, as long as they are properly selected for current.
Applications of the calculator
- Design of electronic circuits.
- Current calculations in parallel circuits.
- Power analysis of element losses.
- Education and learning the principles of Ohm's law.
Summary:The parallel resistor calculator allows you to quickly calculate the equivalent resistance in a circuit. Simply enter element values and the tool will return the result in Ω, along with optional current and power. Useful in electronics, teaching and technical practice.