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Voltage Drop Calculator
Who it's for: Electricians, estimators, and inspectors.
Calculator Inputs
Quick Summary
- Built for: Electricians, estimators, and inspectors.
- Key outputs: Voltage drop (V), Voltage drop (%), and more.
- Use this page for early planning estimates before final code and manufacturer verification.
Inputs
- System voltage (V)
- Phase (single/three)
- Load current (A)
- One-way length (ft)
- Conductor material
- Wire gauge
- Max allowed drop (%)
Outputs
- Voltage drop (V)
- Voltage drop (%)
- End voltage
- Pass/fail vs allowed threshold
- Formula and warnings
How this calculator estimates results
- Uses a built-in approximate conductor resistance table in ohms per 1000 feet for copper and aluminum.
- Converts resistance to ohms per foot, then applies one-way length and phase-specific voltage-drop equations.
- Calculates drop percent from system voltage and compares against the selected allowed threshold.
Cross-check assumptions with Wire Size Estimator for a more complete planning workflow.
Common ranges and tips
- Use measured load current under typical operating conditions when possible.
- Longer runs and smaller conductors can increase voltage drop quickly.
- Review conductor selection with the Wire Size Estimator after checking drop percent.
- Confirm final conductor and overcurrent decisions with code tables and project requirements.
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FAQ
No. This MVP estimate can ignore temperature correction by design, so final calculations should include temperature and installation factors when required.
The equations apply phase-specific factors to one-way distance, while still representing full circuit path effects in the drop estimate.
Use this as an early planning estimate only. Final submittals should use adopted electrical code methods and validated project assumptions.
Consider shorter runs, larger conductors, or load/circuit changes, then verify final design choices with code requirements and equipment specifications.
Disclaimer: Use results for planning only. Final design and installation decisions must follow local code and manufacturer documentation.
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