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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

  • Mike Clary from Grand Junction

    Posted on 9/3/2022

    If I did it right I came out with 96, I am getting a Rockville class D 1000rms 4000peak I have 4gauge wire atm and been curious if I will be good with my new amp

    Commenter image

    Buck Pomerantz from Crutchfield

    on 9/4/2022

    Mike, That amplifier should work fine with 4-gauge power and ground wires.
  • Dustin

    Posted on 8/13/2022

    I have a Db drive 5,000 watt amp. Based on the calculations y'all have to follow I come out with about 483 amps but the size chart doesn't show anything above 300 watts. I'm running 2 powerbass 4xl 15" subs. What size wire should I be using?

    Commenter image

    Buck Pomerantz from Crutchfield

    on 8/15/2022

    Dustin, I can find no reliable RMS power specification for that amp, and so, can only assume that its RMS power is half what is listed - and 1/0-gauge power and ground wire will work.
  • Kenny Simms from Fruitland

    Posted on 8/5/2022

    I believe their is a problem with your formula for figuring proper wire size, you say that a class D amp isn't 100% efficient that it's 75% yet when you divide your example of 400 watts and come up with 533 that's over 100% efficiency. So it seems to me you would want to multiply watts and 75% to come up with 300 watts. That would be 75% efficiency.

    Commenter image

    Buck Pomerantz from Crutchfield

    on 8/5/2022

    Kenny, I'm afraid you've got your math inverted. What the example is saying is that it takes 533 watts from a power source for an amplifier to produce 400 watts of output. Your method says that at 75% efficiency, an amplifier could produce 400 watts from a 300-watt source - which is impossible.

    Posted on 7/23/2022

    Hello, I had difficulty in calculating. please help me. Amp= Helix G four... speaker= Morel maximo Mk2... power cable and speaker cable required...

    Commenter image

    Buck Pomerantz from Crutchfield

    on 7/24/2022

    Osman, That amplifier calls for 4-gauge (American Wire Gauge: AWG) power and ground wires and speakers should use 18- to 14-gauge wires. I don't know what gauge wires are available in your country, however, so you'll have to convert AWG to metric measures on your own.
  • Sean Smith from Spokane

    Posted on 6/29/2022

    If I am pushing 8k-10k watts through 1 speaker wire what size would I need? I have 4 DVC 1 ohm subs wired in series/parallel connected to 2 amps strapped. Each amp is rated 3500 but I've seen them pull almost 5000 on the amp dyno. Do I need 1/0 gauge speaker wire?

    Commenter image

    Buck Pomerantz from Crutchfield

    on 6/29/2022

    Sean, Four DVC 1-ohm subs can be wired together to form four different impedance loads, depending on how they're wired together. 1 - They can be a 0.125-ohm load, coils and subs wired in parallel, allowing up to 283A (amperes) to flow as the result of 10,000 watts of power - and needing 1/0-ga wires to be safe. 2 - They can be a 0.5-ohm load, coils in series and subs parallel, allowing up to 71A to flow as the result of 10,000 watts of power - and needing 4-ga wires to be safe. 3 - They can be a 2-ohm load, coils parallel and subs in series, allowing up to 141A to flow as the result of 10,000 watts of power - and needing 4-ga wires to be safe. 4 - They can be an 8-ohm load, coils and subs in series, allowing up to 35.4A to flow as the result of 10,000 watts of power - and needing 8-ga wires to be safe.
  • Manny from Tucson

    Posted on 6/22/2022

    Hello I have a 1100 w monoblock Boss audio right I'm just looking for the right power size for the app

    Commenter image

    Buck Pomerantz from Crutchfield

    on 6/23/2022

    Manny, If you have the R1100M amp, it takes 8-gauge power and ground wiring.
  • christian

    Posted on 6/20/2022

    Soundstream TRX1000D Amp Soundstream R1.124 Woofer Drive at 2ohm What size of wire i need from the woofer to the box and from the box to the amp and from the battery to the amp I have 8gauge left over can i use it to wire the woofer to the amp all in 8gauge or its to big and it will drain power? For the power i consider use 4gauge The amp use 3x30 amp fuse i will put 100 fuse in the engin bay

    Commenter image

    Buck Pomerantz from Crutchfield

    on 6/21/2022

    Christian, Using huge, over-sized wire doesn't "drain" anything - it will allow larger amounts of current to flow safely. That amplifier calls for a 4-gauge power and ground wire kit. You should use whatever size fuse comes with the kit to protect the wire, according to the manufacturer's specifications. As stated in the article, for subwoofer wiring we recommend using 16-, 14-, or 12-gauge wires. Give us a call, so an Advisor can set you up with the right kinds and amount of wiring for your install.
  • Naythan Demenciuk from Saskatoon, CAN

    Posted on 6/16/2022

    I got my system installed by a local professional. I have a mtx thunder ta7801 amplifier which on paper produces 1200 rms at 1ohm but all the birth sheets online I can find place it between 1600-1700. I have it running 2 alpine type r swr-12 4ohm wired at 1ohm. Its in a truck running about 14 feet of 4 guage wire with a 150 amp in line fuse. The fuse ran for about 30 minutes of hard play and then blew. Should I have went with bigger (even though the shop said 4 is fine) or can I put in a bigger fuse?

    Commenter image

    Buck Pomerantz from Crutchfield

    on 6/16/2022

    Naythan, You should never replace a blown fuse with one of a higher rating - that's dangerous. Take your vehicle back to the installer, so they can correct whatever condition is blowing the fuse. It may be abusive over-driving is the issue, and you really just need a louder system.
  • Pete

    Posted on 5/31/2022

    I have a 2003 Honda Element and will be installing a Skar SK-M500D running 500watts RMS at 1 Ohm hooked to two 4ohm DVC Pyle Power 15's in a sealed box wired for a 1 ohm load. I have power and ground connections at 8 gauge. I am curious if 16 gauge speaker wires are appropriate.

    Commenter image

    Buck Pomerantz from Crutchfield

    on 5/31/2022

    Pete, For wiring subwoofers, we recommend using wires of 12- to 16-gauge in size.
  • 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.
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