Voltage Drop Calculator
Estimate round-trip voltage drop and remaining voltage from current, length, resistance, and supply.
Voltage Drop Calculator Inputs
Results computed instantly — your data never leaves your device.
Voltage Drop Calculator Results
Real-TimeVoltage drop
17.50 V
Remaining voltage
102.50 V
Drop percentage
14.58%
How to Use the Voltage Drop Calculator
- 1
Enter load current in amps.
- 2
Enter one-way cable length in feet.
- 3
Enter conductor resistance in ohms per 1,000 feet.
- 4
Enter supply voltage and review drop and remaining voltage.
Formula & Mathematical Basis
Variable Key
ILoad current in amps
LOne-way conductor length in feet
RConductor resistance in ohms per 1000 feet
📝 The factor of two models a round-trip pair; real installations also depend on conductor temperature, connections, and code requirements.
Step-by-Step Examples
Two-wire run
Scenario: A 10 A load, 100 ft one-way, 1.0 Ω/1000 ft, and 120 V supply.
- 1.Double the one-way length to 200 ft.
- 2.Convert to 0.2 of a 1000-ft resistance unit.
- 3.Multiply 10 × 0.2 × 1.0.
- 4.Compare the 2 V drop with the 120 V supply.
Practical Use Cases
- Screen a cable run during early design.
- Compare conductor resistance assumptions.
Common Pitfalls
- Using total loop length and doubling it again.
- Confusing resistance per foot with resistance per 1000 feet.
- Treating this estimate as a code compliance decision.
Frequently Asked Questions
Does this select wire size?
No; it only estimates voltage drop from the entered resistance.
Is the result code compliant?
No; consult applicable electrical codes and a qualified electrician.
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