Resistor Calculator
Calculate total resistance for series and parallel circuits.
Resistor Values
Ohms (Ω)
Ohms (Ω)
Ohms (Ω)
Total Resistance
Total Resistance
600.000 Ω
600.000 Ω
Connection Type
series
Resistor Values:
R₁ = 100Ω
R₂ = 200Ω
R₃ = 300Ω
Formula:
R_total = R₁ + R₂ + R₃ = 100 + 200 + 300 = 600.000Ω
About This Calculator
The Resistor Calculator calculates the total resistance of resistors connected in series or parallel. In series circuits, resistances add up. In parallel circuits, the reciprocal of the total resistance equals the sum of the reciprocals of individual resistances.
Enter the resistance values of up to three resistors and select whether they are connected in series or parallel. The calculator will compute the equivalent (total) resistance of the combination. This is useful for circuit design and analysis.
Formula & Calculation Method
Resistor Calculation Formulas:
Series Connection:
R_total = R₁ + R₂ + R₃ + ...
Resistances add directly
Parallel Connection:
1/R_total = 1/R₁ + 1/R₂ + 1/R₃ + ...
R_total = 1 / (1/R₁ + 1/R₂ + 1/R₃)
Reciprocal of sum of reciprocals
Two Resistors in Parallel:
R_total = (R₁ × R₂) / (R₁ + R₂)
In series circuits, current flows through each resistor in sequence, so resistances add up. In parallel circuits, current splits between paths, so the total resistance is less than the smallest individual resistance.
How to Use This Calculator
- Enter Resistor Values: Input the resistance values in ohms (Ω) for up to three resistors.
- Select Connection Type: Choose series or parallel connection.
- View Results: See the total equivalent resistance calculated automatically.
- Use Results: Use the calculated resistance for circuit design and analysis.
Frequently Asked Questions
What is the difference between series and parallel connections?
In series connection, resistors are connected end-to-end, so the same current flows through each resistor and resistances add up. In parallel connection, resistors are connected across the same two points, so voltage is the same across each resistor and the total resistance is less than any individual resistance.
How do I calculate parallel resistance?
For parallel resistors, use the formula: 1/R_total = 1/R1 + 1/R2 + 1/R3. Then invert to get R_total. For just two resistors, you can use: R_total = (R1 × R2) / (R1 + R2).
What happens if I leave a resistor value empty?
The calculator will use 0 for empty resistor values. For series connections, 0 doesn't affect the total. For parallel connections, you should enter at least two resistor values.
Can I use this for more than three resistors?
This calculator handles up to three resistors. For more resistors, you can calculate groups of resistors and then combine the results, or use the same formulas with additional terms.
Calculator by
NumCalculators Editorial Team
Multi-disciplinary Expert Team