Voltage Drop Calculator
How much voltage is lost over this wire run, and is it within 3 %?
Single calculationv1.0.0Verified 2026-11-01Runs in your browser
Spec sheet
resistive_voltage_drop · v1.0.0Method
Resistive voltage drop
- 01
R = ρ₂₀·(1 + α(T − 20)) / A - 02
DC / single-phase: Vd = 2 · I · R · L - 03
Three-phase: Vd = √3 · I · R · L - 04
L = one-way length
Limits — read before relying on it
- Resistive (DC) resistance only; reactance and power factor are ignored, which understates drop for large conductors (≥ 1/0) on AC.
- Solid-conductor resistance from the AWG definition; stranded conductors (e.g. NEC Ch. 9 Table 8 for large sizes) run about 1–2 % higher.
- Not an ampacity check and not proof of code compliance.
Sources
- ASTM B258 — AWG diametersstandard
- International Annealed Copper Standard resistivity (1.7241 µΩ·cm at 20 °C)standard