Example: Wire gauge: 12 AWG · One-way length: 100 ft · Current: 15 A · Voltage: 120 V → Voltage drop: 4.76 V (4%).
Voltage at load: 115.2 V
Code guideline: Exceeds 3% — use thicker wire
Frequently asked questions
How do I calculate voltage drop? Enter your numbers above and the result updates instantly. For example: Wire gauge: 12 AWG · One-way length: 100 ft · Current: 15 A · Voltage: 120 V → Voltage drop: 4.76 V (4%).
Is this Voltage Drop Calculator free? Yes — completely free with no sign-up or paywall. It runs entirely in your browser and keeps working offline; the numbers you enter never leave your device.
How accurate is it? It uses the standard published formula for voltage drop. Results are estimates for planning — not financial, tax, medical, engineering, or legal advice.