Voltage Drop Calculator

Free voltage drop calculator for 12V–240V circuits. Uses NEC Table 8 resistance (12 AWG = 1.93 Ω/1,000 ft) to check any run against the 3% guideline.

Voltage Drop Calculator

System Voltage

Wire Gauge

Conductor

One-Way Run Length (ft)

Load Current (A)

Voltage Drop

1.16 V (9.6%)

Voltage at Load

10.84 V

vs 3% Guideline

✗ EXCEEDS — go up a gauge or two

ℹ️ Vdrop = 2 × amps × Ω/1000ft × one-way feet ÷ 1000, resistances from NEC Chapter 9 Table 8. This estimates drop for DIY low-voltage work — ampacity (safe current) is a separate constraint, and mains wiring must follow the NEC with a licensed electrician.