How many amps can 18 AWG wire carry?

For power transmission in a bundle or jacket, 18 AWG copper is conservatively rated around 2.3 amps; as free-air chassis wiring it can handle up to about 16 amps. For security wiring, use the conservative figure — and check voltage drop, which usually limits the run before ampacity does.

What's the difference between chassis wiring and power transmission ratings?

Chassis ratings assume a short single wire in free air that sheds heat easily. Power transmission ratings assume bundled or jacketed conductors over distance, where heat accumulates. Cable runs in walls and conduit are the power-transmission case.

Is ampacity or voltage drop the limit for low-voltage runs?

Almost always voltage drop. A 12V camera run hits a 10% voltage drop long before the wire approaches its thermal ampacity limit — size the gauge with a voltage drop calculator first, then sanity-check ampacity.

Wire Gauge Ampacity Calculator

Enter your load current to get the smallest copper gauge that carries it safely — or look up any gauge's rating. Then check the run with the voltage drop calculator, because on low-voltage runs drop is usually the real limit.

Your load

Load current (A)

Application

Or look up a gauge

Security cable in walls/conduit = “power transmission”. The chassis column applies only to short leads in free air inside an enclosure.

Recommendation

—

smallest gauge for your load

Rating of recommended gauge—

Safety margin—

Lookup result—

Ampacity says the wire won't overheat — it says nothing about the voltage arriving at the device. Check voltage drop for any run over ~50 ft.

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Copper wire ampacity table (AWG)

Gauge	Power transmission	Chassis (free air)	Common security use
24 AWG	0.6 A	3.5 A	Data pairs, Cat5e/6 conductors
22 AWG	0.9 A	7 A	Alarm zones, readers
20 AWG	1.5 A	11 A	Multi-conductor control
18 AWG	2.3 A	16 A	Camera/lock power (18/2)
16 AWG	3.7 A	22 A	Speaker runs, longer power
14 AWG	5.9 A	32 A	Power supply feeds
12 AWG	9.3 A	41 A	Long 24V trunks
10 AWG	15 A	55 A	Heavy DC distribution

Ratings are conservative engineering values for copper conductors. PoE runs are governed differently — 802.3bt on Cat6a bundles is already engineered within the standard.

Frequently asked questions

How many amps can 18 AWG carry?

~2.3 A conservatively for bundled power transmission; up to ~16 A as free-air chassis wiring. Use the conservative number for cable runs.

Chassis vs power transmission ratings?

Chassis = short single wire in free air. Power transmission = bundled/jacketed over distance, which is what in-wall cable runs are.

Ampacity or voltage drop — which limits my run?

On 12/24V systems, voltage drop almost always binds first. Size with the voltage drop calculator, then sanity-check ampacity here.

Low-voltage design questions on a GTA project?

AMT SYSTEMS LTD. engineers the wiring behind every camera, door and panel it installs — sized for load, drop and the service loop you'll need later.

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