---
title: "Calculates the minimum PCB trace width for a given current using the IPC-2221 standard formula. The IPC-2221 empirical equation relates current capacity to cross-sectional area and temperature rise: I = k * dT^0.44 * A^0.725, where k=0.048 for external layers and k=0.024 for internal layers. Supports configurable copper weight (oz/ft^2) and temperature rise. Also computes approximate DC resistance per centimeter. Essential for power delivery, high-current motor drivers, and ensuring PCB reliability. Chain from voltage_divider or impedance_match to verify trace sizing for computed currents."
method: POST
path: "/api/trace_width"
tags: ["pcb"]
---

# Calculates the minimum PCB trace width for a given current using the IPC-2221 standard formula. The IPC-2221 empirical equation relates current capacity to cross-sectional area and temperature rise: I = k \* dT^0.44 \* A^0.725, where k=0.048 for external layers and k=0.024 for internal layers. Supports configurable copper weight (oz/ft^2) and temperature rise. Also computes approximate DC resistance per centimeter. Essential for power delivery, high-current motor drivers, and ensuring PCB reliability. Chain from voltage_divider or impedance_match to verify trace sizing for computed currents.

`POST /api/trace_width`

## Request

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

## Request body

- object
  - `current_amps` number, required: Required current capacity in amperes (A).
  - `copper_oz` number: Copper weight in ounces per square foot. 1 oz/ft^2 = 1.37 mil (34.8 um) thickness. Common values: 0.5, 1, 2.
  - `temp_rise_c` number: Allowable temperature rise above ambient in degrees Celsius. IPC-2221 standard uses 10, 20, or 30 C.
  - `layer` 'external' | 'internal': PCB layer type. External layers dissipate heat better (k=0.048); internal layers use k=0.024.

## Response `200`

Computed result for trace_width

- object
  - `result` object, required
    - `width_mil` number, required: Required trace width in mils (thousandths of an inch).
    - `width_mm` number, required: Required trace width in millimeters.
    - `area_mil2` number, required: Required cross-sectional area in square mils.
    - `resistance_per_cm_mohm` number, required: Approximate DC resistance per centimeter of trace in milliohms, using copper resistivity.
  - `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)