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Amplifier wire gauge chart

How to determine the best size wire for your amp's power and ground

In order to deliver the best sound, an amplifier needs its power and ground wiring to be large enough to accommodate its demand for electrical current. In this article, we'll tell you how to figure out the best wire size for your amplifier.


nderstanding the needs of your car audio system can help you know when to choose 4-gauge wire instead of 8-gauge wire. We've done all the math and specification-matching, so all you need to do is consult our wire size chart below. Of course, if you're looking for a new car amplifier, we list the recommended amp wiring kit with each amp.

What size power and ground wire do I need?

Determing the proper wire gauge (thickness) you should use for your car amplifier's power and ground wiring depends on three factors:

  • how much power you want your system to put out
  • how much current it will try to consume
  • how long the wiring run will be

Add up the total amplifier wattage

First, calculate the total watts RMS output power of your system. Multiply the number of channels by the number of RMS watts per channel. A 4-channel amplifier with 50 watts RMS per channel has a total output of 200 watts.

If you have multiple amps, add up the total RMS wattage figures to arrive at a grand total. Use RMS power ratings only, never peak or max numbers.

We factor in efficiency, voltage, and resistance

Generally speaking, there are two kinds of amplifiers — Class AB and Class D — so there are two formulas for calculating the output power that results from a given current draw due to the different efficiencies of the two technologies. (You can read the detailed explanation below the chart.)

Use the numbers in the column that apply to your amplifier. If you don't know what Class your amplifier is, or have a mix of different amplifiers in a large system, use the Class AB calculations for the safest result.

Wire size calculator

Wire gauge size chart

Note: This chart is for stranded copper wire only. Copper-clad aluminum (CCA) wire cannot handle the amount of current that a copper wire of the same size can. Using CCA wire usually means you'll need a larger size to carry the same amount of current, especially in some of the longer wire runs.

AWG: Please note that our sizes are AWG (American Wire Gauge) sizes. The smaller the gauge number, the larger the wire. For example, 4-gauge wire is larger than 8-gauge wire. 1/0 ("one-aught") is the common name for a 0-gauge wire; 2/0 ("two-aught") for a 00-gauge wire.

Load Capacity: The larger the wire, the more current it can carry, so the amp can put out more power. This is sometimes referred to as the wire's "ampacity." That's the basic premise at play here. The more power in your system and the greater the distance you need it to travel, the larger the wire you need to get it there.

A tinned wire end, with the tin scraped off, exposing the copper underneath

Tinned copper wire with some tin scraped off.

Fusing: For safety, power wires need to be fused as close to the battery as possible. For amplifier wiring kits, always use the fuse the wire manufacturer includes in the kit. For more information, check out our article about Car Amp Fuses.

The formulas we used

Class AB amplifiers: Power output (watts RMS) equals current draw (amperes) times voltage (13.8V) times amplifier efficiency (50%).

Class D amplifiers: Power output (watts RMS) equals current draw (amperes) times voltage (13.8V) times amplifier efficiency (75%).

A more detailed explanation

Here is an explanation about the formulas we used, in case you want more details. Calculating the amplifier's total power is straightforward, but the other parts can be confusing.

Wire is rated for how much current it can carry.

Amplifiers, although rated in watts output, depend on a particular amount of input current to produce a particular amount of output wattage. Different amplifier technologies operate at different efficiencies. There're also resistance factors to consider, due to wire size and length, that affect power delivery.

For the wire gauge chart, we've done all the math for you.

Crutchfield CK4

Crutchfield's 4-gauge power wiring kit works for amplifiers with outputs up to 1100 watts RMS.

Calculating wattage using Joule's Law

Power (watts) equals current (amperes) times voltage (volts).

But no amplifier is 100% efficient

The above formula, by itself, doesn't take into account the inefficiency inherent to power production. That needs to get factored in. An amplifier's efficiency is the ratio of what it puts out divided by what it draws from the electrical system. No amp is 100% efficient, putting out exactly what it draws, nor can an amp put out more power than it draws. The power that doesn't make it to the output terminals is wasted energy that turns into heat. The different amplifier classes produce their outputs with different efficiencies.

Power (watts) equals current (amperes) times voltage (volts) times efficiency (X%).

By factoring in this inefficiency for each class of amplifier, we arrive at the two formulas listed above:

The formula for Class AB amps

For optimum safety, we'll assume a typical Class AB amplifier is 50% efficient, which means about half of the power it generates is turned into audio output while the other half of the power is lost as heat. So if the amplifier is putting out 400 watts, it's actually drawing about 800 watts of power from its source, and the amp's wiring needs to be big enough to handle that draw.

  • A Class AB amplifier's output power (watts RMS) equals its current draw (amperes) times the supply voltage (13.8V) times 50% efficiency.

The formula for Class D amps

A conservatively rated Class D amplifier is about 75% efficient, which means about three quarters of the power it generates is turned into audio output while one quarter of the power is lost as heat. So if the amplifier is putting out 400 watts, it's actually drawing about 533 watts of power from its source, and the amp's wiring needs to be big enough to handle that draw.

  • A Class D amplifier's output power (watts RMS) equals its current draw (amperes) times the supply voltage (13.8V) times 75% efficiency.
Rockford Fosgate RFK1D amplifier wiring kit

Rockford Fosgate's 1/0-gauge dual amp wiring kit comes with a 300-amp fuse and can handle a total output up to 2700 watts RMS.

Automotive voltage is neither 12 volts nor 14.4 volts

And the 13.8? Yes, vehicles have a 12-volt electrical system, but we're assuming that the vehicle is running — which means its alternator will bump up the system voltage to about 13.8 volts. This is a better real-world representation of the vehicle's electrical supply. Dividing by 12 results in a larger number, which could point to a larger wire gauge, but it's often in the same color range in the chart. Manufacturers use 14.4 volts, when they spec their gear, to exaggerate their power ratings.

Resistance increases with wire length

The reason different cable lengths bear different ratings is because the electrical resistance, inherent in all wire, builds up as the cable gets longer, until it forces the voltage to drop below a useable level. At that point, up-sizing the power cable will restore the voltage to its intended level.

Wire size matters for current flow

Finally, according to our tech support guys, the primary performance limitation in most amplifier installations is in the current delivery — either a weak ground or insufficient wire gauge.

Installing too small of a wire gauge results in poor performance, potentially shorter service life of connected components (your amplifier and speakers), and a potential safety hazard.

On the other hand, installing too large a wire gauge doesn't really have any downside, and there is the potential for better performance. Obviously, there's no need to buy 2-gauge wiring when 10-gauge will do. That kind of overkill would be a waste of money. But if the chart could lean either way between two sizes, going with the larger wire size would be the smart choice.

Crutchfield CK12

Crutchfield's 12-gauge wiring kit works for small compact amps and high-power car stereos.

What size speaker wire do I need?

Speaker wiring matters too. The signal and power coming out of your amplifier must not be impeded on their way to your speakers and subs. When you replace or run new speaker wiring, we recommend using:

  • 18-, 16-, or 14-gauge wires for speakers
  • 16-, 14-, or 12-gauge wires for subwoofers

As with the power wire, the longer the run and the more current you're pushing through it, the larger size you should use. For example, if your amp is in the trunk and you're sending 100 watts to your front speakers, 14-gauge speaker wire is a good call. But if the amp is only 50 watts, 16-gauge would be fine.

Stinger PRO Series Speaker Wire

Stinger PRO 16-gauge speaker wire

Let us help you get what you need

Now that you have some idea of how much amp wiring you need, shop our selection of amplifier wiring and accessories. We have amp wiring kits, distribution blocks, and everything else you need. And if you have any questions about putting together a shopping list, contact our advisors via phone or chat. If you want to learn more about amplifier installation, read our Amplifier Installation Guide.

  • Dawson from Iowa

    Posted on 12/26/2023

    I was wondering which wiring kit I should buy. I currently have 2 VD-12 D4 Skar subwoofers and a RP 1200.1D monoblock amp from skar. Any recommendations?

    Commenter image

    Buck Pomerantz from Crutchfield

    on 12/27/2023

    Dawson, That amplifier requires 4-gauge power and ground wires, so choose the 4-gauge kit that has all the accessory wiring you'll also need for your installation. Give us a call, so a Crutchfield Advisor can help you pick the right wiring kit for your system.
  • Jarrett

    Posted on 10/7/2023

    Hey im running the AudioControl ACM-4.300 with the AudioControl PNW-65 for the fronts and rear doors. Can i use 18 Gauge wire over 25 ft at 75 RMS?

    Commenter image

    Buck Pomerantz from Crutchfield

    on 10/9/2023

    Jarrett, That amplifier requires 8-gauge power and ground wires to operate properly. If you're asking about adding new speaker wiring, we recommend using 14- to 18-gauge wire for that.
  • Blake

    Posted on 9/16/2023

    Currently putting together a new system in my station wagon. Amps will be installed in the trunk. Rockford T600-4 and a Rockford T500-1bdcp (running a TOD210). Question, is a 2 gauge CCA cable to a distribution block (in the trunk) with 4 gauge cable to the amps ok? Or would you recommend something else.

    Commenter image

    Buck Pomerantz from Crutchfield

    on 9/16/2023

    Blake, We absolutely do not recommend using CCA (copper-clad aluminum) wires for anything in car audio. The stuff is over-rated in its ability to carry current safely. Please use 4-gauge copper power and ground wires only with these amplifiers - whether 100% oxygen-free or not - for the safety of your vehicle and yourself.
  • Justin H from New Iberia, Louisiana

    Posted on 8/20/2023

    Hi, I just finished mounting my subwoofer and its enclosure in the back of my Jeep and routed 14awg OFC wire between the sub and the amp at the front (about 15 feet or so), but I'm now second guessing my choice of wire size. I'm pushing a 12" marine grade sub pulling about 500w RMS at 2ohm. Is this speaker wire going to be sufficient or should I pull it all out and re-wire with 12awg or heavier? I also took the opportunity to treat all connections in dielectric grease as this will all be exposed to the elements. The grease shouldn't have any impact on sound quality should it?

    Commenter image

    Buck Pomerantz from Crutchfield

    on 8/22/2023

    Justin, 14-gauge speaker wire will work well with your sub. As long as the connections are tightened and making contact with each other properly, applying grease to the outside of the connections won't hurt anything.
  • Sergio from California

    Posted on 8/11/2023

    I'm doing a big 3 with a 290A Alternator on a 2018 Accord and I'm going to swap out my stock battery for a xsD4800 and adding another one in the trunk. I'm also adding (2) Solo X 12s =4,000RMS (2) cxa 1800.1 and 1 Rockford 750x4 for my door speakers can I run 2/0 from Alternator to battery and 2/0 from battery to battery or can I run 2 different 2/0 wires from alternator to batteries and then in the rear put a fuse block with 300A fuses and each 1800.1 amp getting it's own 1/0. Also it would be SHCA tinned OFC wire?? Plz help

    Commenter image

    Buck Pomerantz from Crutchfield

    on 8/11/2023

    Sergio, It certainly won't hurt anything installing 2/0-gauge wiring, if you can get it to fit.
  • Mark from Chisago city

    Posted on 7/26/2023

    Is there a relay that can be put in between the power wire and the battery terminal so that when the car is shut off its not draining the battery?

    Commenter image

    Buck Pomerantz from Crutchfield

    on 7/26/2023

    Mark, All car audio amplifiers feature built-in relays in their remote turn-on circuits that, if wired correctly, will ensure that the amp does not draw any power or current when the vehicle (or even just the radio) is switched off.
  • Marius Rhodén from Drammen

    Posted on 7/23/2023

    Hi. I'm about to install a setup in a new car. Currently have this: - Soundqubed u1-8k - DDm2c - DD715-d4 (x2) Am also about to buy: - DSP with a 4ch amp, or separated (5-800w) - 3-way stage for front - 2-way stage for rear - Lithium bank DD715's for the SQ8k amp. The 2-way stage will include 2x 6-8 inch woofers in rear doors, powered by the DDm2c. Rest is powered by 4ch/dsp. Battery bank will be located in the back of the car, and is located 4-5 meters away from the alternator. So my question is: Do i need more than 2x 1/0 wiring between alt. and battery, and what is recommended fuses to go with that? Mvh. Marius R

    Commenter image

    Buck Pomerantz from Crutchfield

    on 7/24/2023

    Marius, If you expect your system to produce thousands of watts of power, you'll need every one of your amplifiers to have at least one or two 1/0-gauge power and ground connections. And a car electrical system that can support that much current flow.
  • Howard

    Posted on 7/11/2023

    Hello, I am about to install two amps; a Boss class A/B 1600w 2 ohm and a Boss 2600w class A/B, 2 ohm. The 1600 watt is going to run 4 mid range speakers and the 2600w is going to run two 10 in. subs. This is going in a Chevy Tahoe and will range from 5-12ft in length. What is the recommended size speaker wire as well as power wire for my amps. I will be using a two way 0 to 0 fuse distribution block and a 2 way fuse / 6 way block for the ground. If there is anything I need to replace or still need, please let me know. Thanks!

    Commenter image

    Buck Pomerantz from Crutchfield

    on 7/12/2023

    Howard, When you replace or run new speaker wiring, we recommend using 18-, 16-, or 14-gauge wires for speakers and 16-, 14-, or 12-gauge wires for subwoofers. Your two amplifiers may need a 2/0-gauge main power wire.
  • Aaron from Los Angeles

    Posted on 7/6/2023

    Hello, I'm installing alpine r series speakers each at 100 rms powered by an alpine 4 channelx100rms amplifier also adding in a 1,000 watt amp for two 6.5" subwoofers rated at 500 watts rms each. For speakers I'm using ofc 16g wire and subs using ofc 12g wire; likely going to mount under rear seats. Is wiring gauge correct for install or should I use 0g wire to distribution block that has two 4g outputs?

    Commenter image

    Buck Pomerantz from Crutchfield

    on 7/7/2023

    Aaron, You refer to your system's speaker wiring and ask about the power/ground wires? But without knowing precisely what amp and subs you're referring to, we can't help you with accurate advice. If you want a question answered about a system, you must identify the gear by brand names and model numbers so we can get the right information to you.
  • Mike. from Perth

    Posted on 6/22/2023

    Hi Buck, I'm running an old crossfire Bmf1000d mono amp running at 1ohm, recommended to use 4awg and 100 amp fuse, and a Pioneer GM-D8704 4x100 watt amp for the doors. What size cable and fuse do you suggest for the 2 amps, running approx 10 to 15 ft? Also, can a capacitor be used as a distribution block? Thanks mate, appreciate your time

    Commenter image

    Buck Pomerantz from Crutchfield

    on 6/22/2023

    Mike, Using our chart - totaling your Class D amplification at 1400 watts RMS - you should use 2-AWG wire from the battery to a distribution block. That translates to 35mm2 cross-sectional or about a 67-gauge metric wire. Unless your capacitor has multiple beefy wire terminals, we recommend using a separate distribution block.

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