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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.

Understanding 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.

Please note that  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.

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.

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

  • RJ from Phx

    Posted on 10/12/2021

    I have a 2015 civic Si coupe. Currently have: Factory headunit. LOC ,JL slash 250/1 to a JL 10w1v2. With a 4 awg OFC amp kit. I'm going to be hooking up a JL jx 360/4 amp to alpine SPR-60c in the front and undetermined for rears but they will be coaxial. And the slash will continue to power the 10w1v2 1. Can I splice into the harness before the factory amp and use high level inputs into the JX and use the pre outs to the slash amp. ? 2. Will the 4 awg wire from the battery to a distribution block for the slash and jx be enough to allow power to flow to each amp properly with out concern.? The slash amp can use 8awg and the JX uses 4 awg. I'm not good with conversions on this stuff so any help would be great.

    Commenter image

    Buck Pomerantz from Crutchfield

    on 10/13/2021

    RJ, Yes, you can use the signal from your factory radio harness for your 4-channel amp's speaker-level inputs, and the amp's preamp outs for the sub amp's inputs. 4-gauge power wire from battery to distribution block will work for the two amps.
  • John

    Posted on 10/6/2021

    I have a Nakamichi Active Sub with 120w N-power and 1200w max power. Is an 8gauge wiring kit enough for it?

    Commenter image

    Buck Pomerantz from Crutchfield

    on 10/12/2021

    John, That powered sub can use wire as small as 10-gauge for power and ground wiring, but 8-gauge will work okay as well.
  • vtxcalibur from Grayville illinois

    Posted on 9/22/2021

    4800w rms amp and 2 1600w rms subs. 17 foot power wire. 3-4 foot speaker wire.. Extra battery near Amplifier. 1. What size power wire do I need? 2. What size speaker wire? 3. What size fuses for inline main and secondary battery? Thank you for your time

    Commenter image

    Buck Pomerantz from Crutchfield

    on 9/27/2021

    VTX, Without knowing precisely what amp and subs you're referring to, we can't help you with wiring advice. If you don't understand how to figure out what to use for your system, re-read this article or hire a professional installer.
  • Waleed Al Asawi from Misurata Libya ????

    Posted on 8/17/2021

    Thank you for this valuable and useful information. I hope to buy from you, but is there shipping from your side? I have 2 Jeep Liberty 2005 cars how great they are

    Commenter image

    Buck Pomerantz from Crutchfield

    on 8/19/2021

    Waleed, Crutchfield sells gear to customers in the United States and Canada. You'll have to look elsewhere in your country for your purchase. An online search for dealers near you will probably help.
  • david from danvers

    Posted on 8/16/2021

    jl audio rd 900 amp ,17 feet of power wire ,ground to battery as well ,what size wire ,4 ga?

    Commenter image

    Buck Pomerantz from Crutchfield

    on 8/17/2021

    David, JL Audio recommends using 4-gauge power and ground leads and 80-amp fuse
  • Zander Evans from Henderson KY

    Posted on 8/11/2021

    Hello I have a sundown sfb-3000d going to 2 sundown audio sa 12 do Rev 3, 1500 to each sub. What size power wire and what size speaker wire should I use?

    Commenter image

    Buck Pomerantz from Crutchfield

    on 8/12/2021

    Zander, That amp should use 1/0-gauge power and ground wires. Use 16-, 14-, or 12-gauge wires for subwoofers.
  • Billy from Texas

    Posted on 8/2/2021

    I have a Quantum Audio 6500.1 class D amp and two Quantum 12s in a pro box I'm planning on rewiring everything what should I use?

    Commenter image

    Buck Pomerantz from Crutchfield

    on 8/2/2021

    Billy, Such a large amp is off this chart for wire size. But I think you should use the largest-gauge power and ground wires that can fit into the amp's connection terminals - 1/0- or 2/0-gauge wire with a 300A-325A fuse will be safe. For speaker wire, also use the largest wire that fits - 1/0-gauge speaker wire will be the safest.
  • Damian Andrade Jr. from Chicago

    Posted on 7/24/2021

    Hello, I have a JL Audio RD500/1 Monoblock Class D Subwoofer Amplifier, 500 W for my subwoofer and JL Audio XD200/2v2 2 Ch. Class D Full-Range Amplifier, 200 W for my speakers. Which amp kit should I use?

    Commenter image

    Buck Pomerantz from Crutchfield

    on 7/26/2021

    Damian, Use a 4-gauge wiring kit, plus a distribution block that feeds the RD500/1 a 4-gauge wire with a 50A fuse and the XD200/2 an 8-gauge wire with a 30A fuse.
  • Tyler Todd from Ridgecrest

    Posted on 7/22/2021

    Is 8 gauge speaker wire ok for 5000 watts rms

    Commenter image

    Buck Pomerantz from Crutchfield

    on 7/22/2021

    Tyler, 8-gauge speaker wire should be able to handle that much power to a 2- or 4-ohm subwoofer with no problems. A 5000-watt sub system with a total impedance lower than that will need heavier, 4-gauge speaker wires.
  • Grant

    Posted on 7/14/2021

    Hello, I have a Kicker 1200.1 going to 2 Kicker CompR 12's. I already have it wired from my previous setup (only 500 rms) with 4 gauge power and ground with 80 amp fuse as well as 14 gauge speaker wire. Just curious if any of this should be upgraded, thank you.

    Commenter image

    Buck Pomerantz from Crutchfield

    on 7/15/2021

    Grant, That amplifier's specs call for 4-gauge power and ground wire and a 150A fuse. I wouldn't call it an upgrade if you changed your 80A fuse for a 150A fuse, because your 80A fuse is actually safer for you and your car against a short circuit.