AWG ampacity calculator
Pick a wire gauge, an insulation class and copper or aluminum, and read the maximum safe continuous current: 12 AWG copper at 75 °C carries 25 A. Built for electricians, panel designers, makers and training courses. Free in your browser.
- Free
- Runs in your browser
- No sign-up
- Your data stays on your device
Run — free
Worked example
- American Wire Gauge
- 12
- Temp rating
- 75
- Temp rating c
- 75 A
- Material
- Copper
- Ampacity a
- 25
- Table
- nec_310_16_copper_style
American Wire Gauge (AWG) ampacity is the maximum continuous current a conductor of a given size may carry without exceeding its insulation temperature limit under standardized installation assumptions. Electricians, panel designers, makers, and curriculum tools repeatedly look up the same copper and aluminum columns for sixty, seventy-five, and ninety degree Celsius insulation classes—values that map familiar type letters such as TW, THW, and THHN to safe ampere limits for twelve, ten, eight, and larger gauges. Unknown gauges and unsupported gauge-temperature pairs fail with a clear invalid input error rather than a guessed current.
Choosing gauge, insulation temperature rating, and material
Wire gauge is the American Wire Gauge size of the conductor. Everyday branch-circuit copper is often fourteen, twelve, or ten AWG; larger feeders use eight, six, four, two, one, and the aught sizes one-ought through four-ought. Insulation temperature rating is the conductor insulation thermal class in degrees Celsius: sixty for many older TW-style ratings, seventy-five for common THW and many terminations, and ninety for THHN and similar high-temperature insulations.
Only sixty, seventy-five, and ninety are accepted because those are the three columns published in the reference table this product implements. Material defaults to copper; set material to aluminum when you need the aluminum ampacity column set rather than copper-clad marketing shorthand. Small copper gauges such as eighteen and sixteen only have a ninety degree listing in this table; asking for sixty or seventy-five on those sizes is invalid input, not a zero-amp guess.
What you can do with it
Branch-circuit wire selection
Designers enter AWG twelve at seventy-five degrees Celsius copper to confirm twenty-five amp ampacity before comparing against expected load current from a power calculator.
FAQ
Which temperature ratings are supported?
Only 60, 75, and 90 degrees Celsius insulation classes, matching the three common columns (for example TW, THW, and THHN-style ratings).
Is the AWG ampacity calculator free?
The browser tool runs free on your device.
Does this replace the National Electrical Code for permit work?
No. Values are a deterministic NEC Table 310.16-style reference for estimates and education. Always apply the current code edition, corrections, and local authority requirements for construction.
Can I look up aluminum wire?
Yes. Copper is the default, but choosing aluminum switches to the aluminum column of the table. It is meant for true aluminum conductors, not for copper-clad wire sold under that name.
Why can't I choose 60 or 75 °C for 18 or 16 AWG?
Because the reference table lists those small copper gauges only in the 90 °C column. Asking for a lower rating on them gives no result instead of a guessed current.
Related tools
For developers — API access
Everything on this page is available programmatically. This section is for teams who want to wire it into their own systems; everyone else can just use the tool above.
API endpoint
Prefer to automate it? One authenticated POST creates the task; the result comes back by webhook or a signed link. The same capability also runs here on the web, by email and from Telegram — and soon from our app too.
Call it from your stack
curl -X POST https://api.kit.forhosting.com/elec/awg-ampacity \
-H "Authorization: Bearer $KIT_KEY" \
-H "Content-Type: application/json" \
-d '{"gauge":"12","temp_rating":75}'const res = await fetch("https://api.kit.forhosting.com/elec/awg-ampacity", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.KIT_KEY}`,
"Content-Type": "application/json"
},
body: JSON.stringify({
"gauge": "12",
"temp_rating": 75
})
});
const { task_id } = await res.json();import os, requests
res = requests.post(
"https://api.kit.forhosting.com/elec/awg-ampacity",
headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
json={
"gauge": "12",
"temp_rating": 75
},
)
task_id = res.json()["task_id"]<?php
$res = file_get_contents("https://api.kit.forhosting.com/elec/awg-ampacity", false, stream_context_create([
"http" => [
"method" => "POST",
"header" => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
"content" => '{"gauge":"12","temp_rating":75}',
],
]));
$task = json_decode($res, true);body := bytes.NewBufferString(`{"gauge":"12","temp_rating":75}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/elec/awg-ampacity", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)Example request
{
"gauge": "12",
"temp_rating": 75
}Example response
{
"task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
"type": "elec.awg_ampacity",
"status": "queued",
"_links": {
"result": "/tasks/tsk_…/result"
}
}The API is asynchronous: the call returns a task_id immediately and the result arrives by webhook. Polling is capped at 1 req/s per task.
Pricing
Published price — no tokens, no invented credits. A failed task is never charged.
Errors
| HTTP | Code | Meaning |
|---|---|---|
401 | unauthorized | Missing or invalid API key. |
402 | insufficient_balance | Your balance doesn't cover the task price. |
404 | unknown_type | That task type doesn't exist. |
429 | rate_limited | Too many requests. Use the webhook instead of polling. |
Technical notes
This capability performs that lookup deterministically from a JSON body: you send gauge and temperature rating, optionally choose aluminum instead of copper, and receive ampacity in amperes with a stable method label.
Choosing gauge, insulation temperature rating, and material
Send gauge as a JSON string or integer—twelve, ten, or one slash zero—and aliases such as awg and wire_gauge are accepted when documented. Identical inputs always produce identical JSON because the path is a pure table lookup with no network, no random seed, and no wall clock.
Reading ampacity results, errors, and what the table assumes
The lookup follows commonly published NEC Table three-ten-point-sixteen style values for not more than three current-carrying conductors in raceway, cable, or earth; it is a design-estimate and education tool, not a substitute for the current code edition or the authority having jurisdiction. On success the response echoes the normalized gauge key, temp_rating_c as sixty seventy-five or ninety, material as copper or aluminum, ampacity_a as the maximum safe continuous current in whole amperes, unit always A, a table label naming the copper or aluminum column set, and method awg_ampacity_lookup so downstream code can branch without sniffing shapes. Use ampacity_a when sizing breakers relative to conductor ampacity education demos, BOM checkers, or homework oracles; remember that real installations also apply ambient correction, more-than-three current-carrying conductor adjustments, and equipment terminal temperature limits that this reference lookup does not recompute. Unknown gauge strings—metric square millimetres without AWG, nonsense sizes, or gauges outside the published keys—fail with invalid_input and a message that includes unknown gauge. Missing gauge or temp_rating, non-allowed temperature numbers, and aluminum sizes that do not appear in the aluminum table fail the same way and are not charged.
API usage, pricing, workflows, and practical limits
Call the free in-browser AWG ampacity calculator for job-site checks, classroom drills, and quick design sketches without opening a PDF code extract. Keep gauges within the published set eighteen through four-ought for copper and twelve through four-ought for aluminum. Send a JSON body with required gauge and temp_rating, plus optional material when aluminum is needed. Use the prepaid API when an electrical CAD plugin, home-run estimator, e-commerce wire configurator, or training platform needs a stable contract under KIT balance at $0.002 per successful item; validation failures never consume balance after the engine rejects the request. Pair this endpoint with the watts-volts-amps calculator when you next convert branch power into expected load current, then compare that load against ampacity_a before choosing a breaker education example. This product does not derate for conduit fill, ambient above thirty degrees Celsius, rooftop additives, or continuous-load eighty-percent rules—those factors belong in a full design review. Authors shipping SDKs can map ampacity_a and temp_rating_c directly into UI tables that mirror the three insulation columns students see in textbooks, with the same deterministic numbers every request.
Integration use cases
E-commerce and BOM wire pickers
Catalog UIs call the API with gauge and insulation class so product pages show maximum safe continuous current without hard-coding tables in every storefront.
Classroom and exam oracles
Instructors pin golden JSON for copper fourteen AWG at sixty degrees and intentional unknown-gauge errors that must fail with invalid_input.
Technical questions
How do I look up AWG ampacity with this calculator?
Send JSON with gauge (for example "12") and temp_rating (60, 75, or 90). The response includes ampacity_a in amperes for copper by default; set material to "aluminum" when needed.
What happens if the gauge is unknown?
The request fails with invalid_input and a message that the gauge is unknown or unsupported for the chosen material. Validation failures are not charged.