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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.

U

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

  • 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.
  • 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.

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