Resistor Series/Parallel Calculator
Total resistance for two resistors in series or parallel.
Enter your values
Enter the resistor 1 in ohms.
Enter the resistor 2 in ohms.
Results update instantly as you type — no submit needed. Your values are remembered on this device, and the shareable link reopens the calculator with exactly these numbers.
- Series total
- 690 Ω
- Parallel total
- 149.86 Ω
Quick answer
Series: R = R1 + R2. Parallel: R = (R1 x R2)/(R1 + R2).
R_series = R1+R2, R_parallel = R1R2/(R1+R2)
At a glance
| What it does | Total resistance for two resistors in series or parallel. |
|---|---|
| Category | Engineering |
| Inputs needed | Resistor 1, Resistor 2 |
| Main output | Series total |
| Formula | R_series = R1+R2, R_parallel = R1R2/(R1+R2) |
| Cost | Free — no sign-up, no download |
How to use the Resistor Series/Parallel Calculator
- 1Enter the two resistor values.
- 2Series resistance simply adds up.
- 3Parallel resistance is always lower than the smallest individual resistor.
Inputs explained
- Resistor 1(ohms)
- Enter the resistor 1 in ohms.
- Resistor 2(ohms)
- Enter the resistor 2 in ohms.
Worked example
Using the values the calculator loads with:
Inputs
- Resistor 1220 ohms
- Resistor 2470 ohms
Results
- Series total690 Ω
- Parallel total149.86 Ω
Frequently asked questions
Why is parallel resistance lower?
Adding a parallel path gives current more routes to flow, reducing overall resistance.
How do I combine three or more resistors?
Combine two at a time, or for equal parallel resistors divide the value by the count.
What do I need to enter into the Resistor Series/Parallel Calculator?
Just 2 values: resistor 1, resistor 2. Every field starts with a realistic example, so you can change one number at a time and watch the result update instantly.
How does the Resistor Series/Parallel Calculator work out the answer?
Series: R = R1 + R2. Parallel: R = (R1 x R2)/(R1 + R2). It applies the formula R_series = R1+R2, R_parallel = R1R2/(R1+R2) and shows the working so you can check each step by hand.
Is the Resistor Series/Parallel Calculator free, and do I need an account?
It is completely free with no sign-up, no download and no usage limit. Everything is calculated in your browser, so the numbers you type never leave your device.
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.