Voltage Drop Calculator
Estimate voltage drop in electrical circuits using NEC data, estimated resistance, or custom values
NEC Data
Estimated Resistance
Custom
📚 Calculate with NEC Data
Calculate voltage drop using resistance and reactance data from the National Electrical Code (NEC)
V
A
ft
PF
📏 Calculate with Estimated Resistance
Calculate voltage drop using resistance estimated from wire size
V
A
ft
⚙️ Custom Calculation
Calculate voltage drop using custom resistance or impedance values
V
A
ft
Ω
Ω
PF
Voltage Drop Results
Voltage Drop
5.8 V
Actual voltage at load
Percentage Drop
4.83%
Of source voltage
Power Loss
116 W
In the circuit
Wire Resistance
0.48 Ω
Total circuit resistance
ℹ️ About Voltage Drop
Voltage drop is the reduction in voltage in an electrical circuit between the source and load. Excessive voltage drop can cause equipment malfunction, inefficiency, and safety hazards.
Key considerations:
- NEC recommends maximum 3% voltage drop for branch circuits and 5% for feeder and branch circuits combined
- Factors affecting voltage drop: wire size, length, material, current, and temperature
- AC circuits are affected by both resistance and reactance (inductive effects)
- Larger wire sizes reduce voltage drop but increase installation costs
Formulas used:
Single Phase: Vdrop = 2 × I × L × (R × cosθ + X × sinθ) / 1000
Three Phase: Vdrop = √3 × I × L × (R × cosθ + X × sinθ) / 1000