Voltage Drop Calculator

System

DC/1-Phase use 2× length (round-trip). 3-Phase uses √3 × I × R × L.

Nominal Voltage (V)

Load Current (A)

One-Way Length

Enter one-way run length of the circuit.

Conductor / Mode

AWG (Copper)

Uses DC resistance at 20 °C (Ω per 1000 ft).

Custom Resistance (Ω per 1000 ft)

For aluminum or special cables, enter manufacturer’s resistance@20 °C.

Drag & drop a JSON config here (or click) to prefill. Nothing is uploaded.

Keys recognized: system, voltage, current, length, unit, material, awg, r1000

Voltage Drop – Quick Cheat Sheet

DC / 1-Phase AC: V_drop = I × (R/ft) × (2 × L) (round-trip length).
3-Phase AC (line-to-line): V_drop ≈ √3 × I × (R/ft) × L.
Resistance source: Copper AWG uses DC resistance @ 20 °C (Ω/1000 ft). For aluminum or specialty cable, use “Custom”.
% Drop: V_drop / V_nom × 100%. Many designers aim for ≤3% on branch circuits and ≤5% overall (verify local code/spec).
Length: Enter one-way run length; the math handles round-trip/√3 as needed.

Notes & edge cases

Temperature, strand construction, and reactance can change real-world drop—manufacturer data is best.
For aluminum or non-standard cables, switch to Custom resistance and enter Ω/1000 ft from the datasheet.
Three-phase formula shown is the common resistive approximation for balanced systems.