---
title: "Determine minimum wire gauge using NEC Table 310.16 ampacity ratings with full derating. Looks up base ampacity for copper or aluminum conductors at 60°C, 75°C, or 90°C insulation rating, then applies NEC 310.15(C)(1) ambient temperature correction and NEC 310.15(C)(2) conductor count adjustment. Automatically applies the 125% continuous load factor per NEC 210.20(A) when flagged. Returns the minimum AWG that meets the derated requirement, plus a comparison table of all gauges. Different from wire_gauge which focuses on voltage drop — use both together for complete wire sizing. Essential for residential panels, commercial feeders, solar arrays, and EV charging installations."
method: POST
path: "/api/wire_ampacity"
tags: ["power"]
---

# Determine minimum wire gauge using NEC Table 310.16 ampacity ratings with full derating. Looks up base ampacity for copper or aluminum conductors at 60°C, 75°C, or 90°C insulation rating, then applies NEC 310.15(C)(1) ambient temperature correction and NEC 310.15(C)(2) conductor count adjustment. Automatically applies the 125% continuous load factor per NEC 210.20(A) when flagged. Returns the minimum AWG that meets the derated requirement, plus a comparison table of all gauges. Different from wire_gauge which focuses on voltage drop — use both together for complete wire sizing. Essential for residential panels, commercial feeders, solar arrays, and EV charging installations.

`POST /api/wire_ampacity`

## Request

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

## Request body

- object
  - `current_amps` number, required: Required circuit current in amperes. Use 125% of continuous load per NEC 210.20(A).
  - `conductor` 'copper' | 'aluminum': Conductor material. Copper has higher ampacity; aluminum is lighter and cheaper for large feeders.
  - `insulation` '60' | '75' | '90': Insulation temperature rating in °C. 60=TW/UF-B, 75=THW/THWN/XHHW (most common), 90=THHN/THWN-2.
  - `ambient_temp_c` number: Ambient temperature in °C. NEC base is 30°C. Higher temps require derating. Typical: 30 (indoor), 40 (attic/hot), 45+ (rooftop conduit).
  - `conductors_in_raceway` number: Number of current-carrying conductors in a single raceway or cable. More than 3 requires derating per NEC 310.15(C)(2).
  - `continuous_load` boolean: Whether the load operates continuously (3+ hours). NEC requires 125% sizing for continuous loads. Set false for intermittent loads.

## Response `200`

Computed result for wire_ampacity

- object
  - `result` object, required
    - `minimum_awg` number, required: Minimum AWG wire gauge that meets the derated ampacity requirement.
    - `minimum_awg_label` string, required: Human-readable AWG label (e.g. '4/0', '12', '2').
    - `base_ampacity_a` number, required: Base ampacity from NEC 310.16 before any derating, in amperes.
    - `derated_ampacity_a` number, required: Final ampacity after applying ambient temperature and conductor count correction factors, in amperes.
    - `required_ampacity_a` number, required: Ampacity required to carry the load (includes 125% factor if continuous).
    - `ambient_correction` number, required: Ambient temperature correction factor applied (1.0 at 30°C).
    - `conductor_count_correction` number, required: Conductor count correction factor (1.0 for 3 or fewer).
    - `insulation_label` string, required: Insulation rating description.
    - `all_gauges` object[], required: All available gauges with their ampacities for comparison.
      - `awg` number, required: AWG gauge number
      - `awg_label` string, required: Human-readable AWG label
      - `base_ampacity_a` number, required: NEC 310.16 base ampacity
      - `derated_ampacity_a` number, required: Ampacity after derating
      - `sufficient` boolean, required: Whether this gauge meets the requirement
  - `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)