calc.engineer / Solar & Power / Voltage Drop

Voltage Drop v1.0.0

Calculates voltage drop across a conductor run given current, wire length, AWG gauge, system voltage, and conductor material (copper or aluminum). Computes round-trip resistance, voltage drop in volts and percent, voltage at the load end, power dissipated in the wire, and NEC compliance flags (3% max for branch circuits, 5% max for feeders). Use this after wire_gauge to verify a specific gauge meets requirements, or to evaluate an existing installation. Critical for solar panel string wiring, EV charger circuits, low-voltage lighting, and any long DC or AC cable run where resistive losses matter.

← from wire_gaugefeeds solar_sizing →
Load current in amperes (A)
One-way wire length in meters
Wire gauge in AWG (e.g. 14, 12, 10; use negative for large gauges: -3 = 4/0)
System voltage (V)
Conductor material: copper or aluminum
Fill in the inputs and Compute to see the structured result.

From an agent (MCP) or the API

curl -X POST https://calc.engineer/api/voltage_drop \
  -H "Content-Type: application/json" \
  -d '{"current_amps": …, "wire_length_m": …, "wire_gauge_awg": …}'

MCP: connect to https://calc.engineer/mcp and call voltage_drop.

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