---
title: "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."
method: POST
path: "/api/voltage_drop"
tags: ["power"]
---

# 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.

`POST /api/voltage_drop`

## Request

- Base URL: `https://calc.engineer`
- URL: `https://calc.engineer/api/voltage_drop`
- Auth: none declared

## Request body

- object
  - `current_amps` number, required: Load current in amperes (A)
  - `wire_length_m` number, required: One-way wire length in meters
  - `wire_gauge_awg` number, required: Wire gauge in AWG (e.g. 14, 12, 10; use negative for large gauges: -3 = 4/0)
  - `voltage_v` number, required: System voltage (V)
  - `conductor` 'copper' | 'aluminum': Conductor material: copper or aluminum

## Response `200`

Computed result for voltage_drop

- object
  - `result` object, required
    - `voltage_drop_v` number, required: Voltage drop across the conductor run (V)
    - `voltage_drop_pct` number, required: Voltage drop as a percentage of system voltage
    - `voltage_at_load_v` number, required: Voltage at the load end (V)
    - `resistance_ohm` number, required: Total round-trip conductor resistance (ohm)
    - `power_loss_w` number, required: Power dissipated as heat in the conductor (W)
    - `compliant` boolean, required: True if voltage drop is within NEC limits (<=3% branch, <=5% feeder)
  - `tool` string, required
  - `version` string, required
  - `computed_at` string, date-time, required
  - `chain` object, required
    - `feeds` unknown[]
      - unknown
    - `accepts_from` unknown[]
      - unknown

## Other responses

- `400`: Validation error or invalid JSON
- `404`: Tool not found

---

[API](https://skmtc.dev/calc/apis/calc-engineer-api.md) · [All operations](https://skmtc.dev/calc/apis/calc-engineer-api/llms.txt) · [OpenAPI document](https://skmtc.dev/calc/apis/calc-engineer-api/revisions/8830480ec488?raw)