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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

  • Brad

    Posted on 12/5/2022

    Hello, love your articles. I have an Audiobahn A12001DT Class D monoblock that specs as 1200w @ 1ohm and 750w RMS at 2 ohms. If I wire my single 500w RF punch 4ohm DVC in parallel to present a 2 ohm load to the amp, am I safe to wire it with 8 gauge copper based off 750w? I am confused as to whether an amp will actually draw less power with the speakers wired at 2 ohms vs 1 ohm, or if it just puts out less power but still has the same draw on its power source. Yes I realize that amp is a bit beefy for that sub, I will address proper settings so as to not blow it later.

    Commenter image

    Buck Pomerantz from Crutchfield

    on 12/6/2022

    Brad, We do not recommend powering a subwoofer with more watts RMS than it's rated for - that constitutes abusive usage and damage will not be covered by a warranty. An amplifier's power draw from an electrical source is a product of its output and efficiency. A D-Class amplifier - conservatively considered here to be 75% efficient - that puts out 1200 watts RMS will draw about 1600 watts RMS. That same amplifier wired to put out 750 watts RMS will draw about 1000 watts RMS from the electrical source of power. As the article and chart indicate, your amplifier needs 4-gauge power and ground wires to operate properly.
  • Alex from Louisville, KY

    Posted on 11/29/2022

    I have 2 250watt rms svc subs. Both are the same brand (kenwood) and sub which are rated at 4ohms. I was thinking about running them in parallel as 2 ohm amps are more common it seems, would I be looking at getting a 500watt rms amp? If I should get the 500rms amp at 2ohm should I get 4gauge wire for power and ground? Probably 12 gauge speaker wire to install the subs to the box?

    Commenter image

    Buck Pomerantz from Crutchfield

    on 11/30/2022

    Alex, Two SVC 4-ohm subs rated for 250 watts RMS each will work best with an amplifier that can put out up to 500 watts RMS at 2-ohms. Such an amplifier will probably only need 8-gauge power and ground wires, but different brand amps have different requirements and you'll need to use what the amp manufacturer recommends. As for subwoofer speaker wiring: 16-, 14-, or 12-gauge wires will work well.
  • Troy Godwin from SUFFOLK

    Posted on 10/30/2022

    So is the amperage determined at the closes battery if I'm running a multiple battery setup?

    Commenter image

    Buck Pomerantz from Crutchfield

    on 10/31/2022

    Troy, The amperage discussed here is actually a measure of the maximum current flow, or draw, possible for an amplifier or amplified system. You determine that by adding up how much current your amplifiers are capable of outputting and then take into account their efficiency to estimate the total draw from the power supply. The amperage capabilities of your batteries are determined by the manufacturer's specs, and only become relevant to car audio when they can't support the current draw of the amps connected to them.
  • David A Williams from Cheltenham

    Posted on 10/17/2022

    Hello, I'm running a MTX Thunder Elite 1501D 3000w max 1000w RMS to an (OG) MTX 9500 DVC 4-ohm 12". In my last car I ran 0 gauge but it's a pain to run that thru the car. I also plan on getting a 100 RMS × 4 amp for the doors. From the battery to the amp (with this amp, you go thru it first THEN go to the capacitor) do I need to run Zero (0) again? Thank you.

    Commenter image

    Buck Pomerantz from Crutchfield

    on 10/17/2022

    David, For those two amplifiers, you should use 0-gauge or 2-gauge power and ground cables. 4-gauge will probably work, but won't support full-power output.
  • T from Tacoma, WA

    Posted on 10/5/2022

    I have the following... JL Audio HD750/1 Monoblock Class D Wide-Range Amp, 750 W and 12W6v3-D4 12-inch (300 mm) Subwoofer Driver, Dual 4 O

    Commenter image

    Buck Pomerantz from Crutchfield

    on 10/5/2022

    T, Make sure you set that amplifier's gain as low as possible, because that 750-watt amp could blow that 600-watt rated sub.
  • Darin Teasley from REYNOLDSBURG

    Posted on 9/30/2022

    My a p is a jp95 I plan to use 4 speakers at 120 watts, pioneer z65c and morel maximo and 700 watts to sub. Alpine type r 10

  • Darin Teasley from REYNOLDSBURG

    Posted on 9/29/2022

    I have jp 95, it s 120 RMS x4 at 4ohms, 700x1 at 2Ohms. Will 4 gauge wire work.

    Commenter image

    Buck Pomerantz from Crutchfield

    on 9/30/2022

    Darin, Without knowing precisely what amp (brand name and model number) you're referring to, I can't help you with accurate advice. If your amplifier can actually put out a total of 700 watts RMS, 4-gauge power and ground wires will work well.
  • Crystal from Bellflower

    Posted on 9/26/2022

    If I have 2 15 l7 subsonic kickers what gage should I use 3500 watt amp it has 4 gage everything melted don't no why did shop mess up Thanks for your time

    Commenter image

    Buck Pomerantz from Crutchfield

    on 9/28/2022

    Crystal, If your amplifier really can put out 3500 watts RMS, it would need 00-gauge power and ground wires - but not knowing exactly which amplifier or subwoofers you have make it impossible to give accurate advice on how to wire them together. If you want a question answered about your system, you must identify your equipment by brand names and model numbers.
  • 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.
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