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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 operate correctly, an amplifier needs its power and ground wiring to be large enough to accommodate its demand for electrical current. What wire gauge (thickness) to use for power cabling depends on how much current your system will try to consume, and on how long the wiring run will be.


nderstanding the needs of your system can help you know when to choose 4-gauge wire instead of 8-gauge wire. Do a little bit of math and then 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. 

The formulas for calculating current draw

To determine the approximate current draw (in amperes) of your amplifier, you must first calculate the total power of the system. Multiply the number of channels by the number of RMS watts per channel. If you have multiple amps, add up the total RMS power figures to arrive at a grand total.

Generally speaking, there are two kinds of amplifiers — Class D and Class AB — so there are two formulas for calculating current draw. (You can read the detailed explanation below the chart.) You use the formula that applies to your amplifier. If you don't know what Class your amplifier is, use the Class AB calculations for the safest result.

Class D amplifier: total RMS Wattage divided by 0.75 Amp Efficiency divided by 13.8 Volts equals Current Draw in Amperes

Class AB amplifier: total RMS Wattage divided by 0.50 Amp Efficiency divided by 13.8 Volts equals Current Draw in Amperes

The resulting figure is your system's approximate maximum current draw, whichever kind of amplifier you have. Compare this number to the numbers in the "Amperes" column in the chart below. Now figure out the cable length you'll need — that's the distance from your battery to the amplifier's mounting location. Cross-reference these two figures in the chart to determine which gauge of cable you need.

AWG: Please note that our sizes are AWG (American Wire Gauge) sizes. The smaller the gauge number, the larger the 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. This is sometimes referred to as its "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. 

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.

A more detailed explanation

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

Calculating Current: Joule's Law

Current (Amperes) equals Power (Watts) divided by 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.

Current (Amperes) equals Power (Watts) divided by Amp Efficiency (X%) divided by Voltage (Volts)

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

The formula for Class D amps

A typical 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 Current Draw equals its RMS output Wattage divided by 75% Efficiency divided by 13.8 Volts

The formula for Class AB amps 

A typical Class AB amplifier is about 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 Current Draw equals its RMS output Wattage divided by 50% Efficiency divided by 13.8 Volts

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.

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. 

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 — the info is at the top of this page. If you want to learn more about amplifier installation, read our amplifier installation guide

  • Anthony

    Posted on 5/8/2022

    I have a alpine s-a60m amp running at 2ohms, rated at 600w x1 but birth sheet says 850w x 1 @ 2 ohms. Currently have 8 gauge cca power wire but only 5 feet from the battery with a 80 amp fuse. Is this acceptable?

    Commenter image

    Buck Pomerantz from Crutchfield

    on 5/9/2022

    Anthony, That wiring is very unsafe. I recommend replacing that way-too-thin aluminum wire with 4-gauge OFC (copper) wire, along with at least a 60A inline fuse. Give us a call so an Advisor can help you get the right wiring kit for your installation.
  • Miguel Pinho from Arouca

    Posted on 4/14/2022

    good afternoon! I have a single question... I have a JBL club A600 amp wich makes 600w x1 at 2ohm and 350w x1 at 4ohm. My subwoofer is a JBL club 1200B that works at 4 ohms. given this I dont know what number i should use to do the account, the 350w since my sub works with 4ohm or the 600w since its the highest rms wattage my amp provides. can you help me? Thanks for the attention! :D

    Commenter image

    Buck Pomerantz from Crutchfield

    on 4/14/2022

    Miguel, Amplifiers react differently to different loads wired to their outputs. Your amplifier will put out 600 watts RMS to a 2-ohm sub, and 350 watts RMS to a 4-ohm sub.
  • Matt from Eugene OR

    Posted on 3/8/2022

    When measuring the length of wire needed. Do you just measure from the positive to the amps or do you also take into consideration the length from the amp to the grounding point?

    Commenter image

    Buck Pomerantz from Crutchfield

    on 3/9/2022

    Matt, Usually, just the length of the positive wire is considered, because in car audio, the ground wire is normally a short wire from the amp to the chassis - and the extra length won't contribute much to the over-all resistance to current flow. If the ground is run all the way to the battery, like in marine applications, then you should add in that length for your calculations.
  • Christopher from Nanticoke, PA

    Posted on 2/17/2022

    Would I be able to safely power these two amps in off of 4 gauge OFC Wire in this configuration? Amp 1) D-6.1200 running @ 125rms x6 (4ohm) Amp 2) LC-1.800 running @ 500rms (4ohm) If I'm doing the math right, I get 1250 RMS. Divide that by the efficiency of a typical class D Amp and then again for Voltage supplied, I arrive at 120.7 amps. Basing it off the chart above I should be within spec for a 15 to 19 foot run. I'll be around 19 as I will connect to a distribution block w/ 4ga. in and two 4 ga. out. Also, 120 amps would be the highest draw? I suspect a constant draw at "normal" listening levels would be much lower than that?

    Commenter image

    Buck Pomerantz from Crutchfield

    on 2/17/2022

    Christopher, When figuring power wire size, we usually use the worst case highest power scenario to be safe, so that no wire will ever get overloaded. Those amplifiers can actually put out a lot more power than what you're figuring with - but that's okay. If those amplifiers were both hooked to 2-ohm speakers, they'd be able to put out a total of 2000 watts RMS, drawing about 193A, and needing a 1/0-gauge main power wire. But if you're not going to use anything but 4-ohm loads, you'll draw about 121A at maximum demand - when the input signal and your taste calls for full power - needing a 4-gauge power wire to be safe for a 19-foot run.
  • Tyler from Alamogordo

    Posted on 1/30/2022

    Great guide, always was curious on whether a 8 gauge was enough for amplifier wiring. Thank you very much Crutchfield.

  • Jerry Kamis

    Posted on 1/5/2022

    Hi, I want to use a Rockford's R2 750x5 for this setup : 50Wx4 + 200Wx1 at 4 ohm. Should I go with the recommended 120A fuse and 4 AWG wire?

    Commenter image

    Buck Pomerantz from Crutchfield

    on 1/5/2022

    Jerry, Yes. You should always use the recommended wire size and fuse for your amp.
  • Travis B from Charlotte

    Posted on 1/4/2022

    It was with only the two amps. The way it was written, I can see how it was confusing. Yes, Qty 1 (R2-750x1) Qty 1 (R2-500x4) I got the 77 Amps as well. I referenced the chart first, just wanted to make sure I wasn't missing something. Didn't want to pay double the price for wire that was overkill. Thank You Buck.

  • Travis B from Charlotte

    Posted on 1/2/2022

    2 Rockford Fosgate Amps R2-750x1 will be 500rms at 2ohm R2-500x4 will be 75rmsx4 4ohm I've done the math on everything, and come up with around 75amps, and a 4awg power wire for 15ft from battery to amps. But looking for more experienced input. Just making sure I'm correct on everything. I've read/had some input to just go to a 1/0 wire. But don't think I'm gaining/losing anything for over 2x the price.

    Commenter image

    Buck Pomerantz from Crutchfield

    on 1/4/2022

    Travis, I don't know how you figured it, but with two R2-750x1 amplifiers and one R2-500x4, the total draw would be around 126A. With one R2-750x1 and a R2-500x4, 77A. In either instance, a 4-gauge main power wire will work well.
  • Everton Campbell from DORAL

    Posted on 12/21/2021

    I am running 4 amplifiers they all require 4 gauge power and ground, should I use 2-4 aught cable for ground? As the all run through a distro block

    Commenter image

    Buck Pomerantz from Crutchfield

    on 12/22/2021

    Everton, Without knowing precisely what amplifiers you're referring to, we can't help you with 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.
  • Kent from Goodland

    Posted on 12/17/2021

    I am replacing my current amp, which has failed, with a Pioneer GM-A6704, (4 channel 60x4 rms) 1000 watt amp. I will be powering 4 Kicker 46CSC684 2 way speakers with the amp. Currently I have a 14 foot, 10 gauge power wire and a 2 foot, 10 gauge ground wire installed. Although, I feel like I am extremely border line between 10 and 8 gauge can I get by with my 10 gauge set up? I desire not to run new wires if I don't have to. As a mid aged relative newbie to car audio any advice is appreciated and thank you!

    Commenter image

    Buck Pomerantz from Crutchfield

    on 12/17/2021

    Kent, You'll probably be alright using 10-gauge power and ground wires for that amp. The only problem you may run into is that the amp won't easily produce its highest output because of current-flow limits of the wires. But I doubt you'll ever notice it.

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