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

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
Jj from Durango
Posted on 1/21/2023
What's the order of operations? W / .5 / 13.8 Or W / (.5 / 13.8)
Buck Pomerantz from Crutchfield
on 1/23/2023
Lamont Jackson from Modesto
Posted on 1/11/2023
I have a Kenwood KAC- 8452 that will be pushing 70watts x 4 @ 4ohms and also a Kenwood KAC-X10D mono that will be pushing 600watts x 1 @ 2ohms. Car is a Camry so possibly less than 15ft run from battery to trunk. Question is, can I get away with a 4gage power wire for one run from battery to trunk and use a distribution block to feed both amps? If so, which wires and gauges do you suggest? What do you feel is a good method to power both those amps safely. Thanks
Buck Pomerantz from Crutchfield
on 1/12/2023
Charles from Carrollton
Posted on 1/1/2023
I have three JL 10tw3-4 ohm subs that are powered by a Kicker CXA1800.1 amp. I took it to a shop and the guy who installed it stated that he wired it to 1.3 ohms but is having issues with the amp not being able to supply enough power at about 75% volume. Is this amp powerful enough to push those three 400 watt rms sub at 1.3 ohms or should I wire them back up to 2 ohm?
Buck Pomerantz from Crutchfield
on 1/3/2023
Ryan race from Cincinnati
Posted on 12/17/2022
Hey man , I have a kicker -cx1200w class d mono Model #46cxa12001 amp and 2 kicker 12 inch solo baric L7 in a enclosure, model #44DL7S122. So now i have to 2 questions. My 1st is : I haven't installed anything jus yet but is that amp a good enough size for those speakers ? And my 2nd is : what size gage wires I need for this setup ? 4?
Buck Pomerantz from Crutchfield
on 12/21/2022
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.
Buck Pomerantz from Crutchfield
on 12/6/2022
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?
Buck Pomerantz from Crutchfield
on 11/30/2022
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?
Buck Pomerantz from Crutchfield
on 10/31/2022
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.
Buck Pomerantz from Crutchfield
on 10/17/2022
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
Buck Pomerantz from Crutchfield
on 10/5/2022
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