Series and parallel resistance equations
Series resistances add directly; parallel conductances add.
Series: Req = R1 + R2 + … + RnParallel: 1 / Req = 1/R1 + 1/R2 + … + 1/Rnwhere:
- Req
- Equivalent resistance[Ω]
- Rn
- Individual resistor value[Ω]
Power and voltage ratings must be checked for every individual resistor.
How to use the Series and Parallel Resistor Calculator
Calculate equivalent resistance, current, and voltage or current division for up to four resistors. Start by choosing the operating mode, then enter values from nameplates, measurements, or project documents in the units shown. The result updates immediately and keeps intermediate quantities visible for review.
- Confirm the system and calculation mode.
- Enter measured or manufacturer-rated values.
- Review the primary result and intermediate metrics.
- Continue with the related protection or equipment-selection checks.
Calculation method and validation
The equations and symbol definitions above show the complete calculation basis. Inputs are checked before calculation so zero, negative, incompatible, or physically impossible combinations are flagged instead of silently producing a misleading result.
How to interpret the result
Use the main result as a starting value and read every supporting metric. Ideal linear resistors All four entered resistor values are connected A passing or recommended result means the entered mathematical conditions are satisfied; it does not certify the complete installation or a particular product combination.
- Ideal linear resistors
- All four entered resistor values are connected
Selection limits and next checks
Check resistor voltage and power ratings before construction. Compare the output with the current applicable standard, local rules, exact VIOX product datasheet, environmental conditions, protection coordination, and the engineer's project requirements before procurement or installation.
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Assumptions
- Ideal linear resistors
- All four entered resistor values are connected
Important Warnings
- Check resistor voltage and power ratings before construction.