Voltage Drop Calculator — Wire Length & Gauge | WireStandard

Calculate voltage drop for any wire gauge and length. See drop in volts and percentage with pass/fail for NEC 3% and 5% thresholds.

Current (A)

System Voltage (V)

One-way Wire Length (m)

Wire Gauge

Use AWG

Enter mm²

Phase

Single-phase (2-wire)

Three-phase (balanced)

Voltage Drop

Voltage Drop %

Conductor Temperature

60°C (NEC 60°C — THWN)

75°C (NEC 75°C — THWN-2/THHN)

90°C (NEC 90°C — XHHW-2)

Accuracy ±3%: formula uses idealized IACS copper resistivity (ρ=0.01724 Ω·mm²/m at 20 °C) with a linear α=0.00393/°C temperature correction. Published NEC Chapter 9 Table 8 DC values (stranded, uncoated) are 1–3% higher. For safety-critical installations add a 10% margin on the drop % or consult a licensed engineer.