Resistor Series / Parallel Calculator
Enter two positive resistor values and choose series or parallel wiring.
A QUICK WALKTHROUGH
How to use this tool
- Enter R1 and R2 in ohms.
- Choose series or parallel.
- Calculate the equivalent resistance.
Formula
Series: Req = R1 + R2. Parallel: Req = (R1 × R2) ÷ (R1 + R2).
Input boundary
Values must be finite and greater than zero. This ideal calculation excludes resistor tolerance, temperature, wiring, and meter effects.
Local calculation
Values are validated and calculated in your browser and are not uploaded or stored.
GOOD TO KNOW
Common questions
What unit should I enter?
Enter both values in ohms (Ω); use decimal notation for kΩ or MΩ after converting to ohms.
Can I use zero or negative resistance?
No. This two-resistor calculator accepts only finite positive values.
Is this a circuit simulation?
No. It is an ideal equivalent-resistance calculation and does not model power, tolerance, or frequency effects.