What Gauge Wire Do I Need For Amp? EXPLAINED!

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If you like music, and installing your own audio systems in your vehicle you will need to do a little math, unfortunately. Armed with a simple formula you can be sure that your system will not be restricted because the wires are not able to deliver the needed power to your amp.

Equally problematic is when the wires are too large, and you have unneeded cost with larger wire than you need and possible overpowering issue as well.

The Formula

STEP 1. First, you need to determine the current draw in amperes of your amplifier. To do that you need the total power of the system, multiply the number of channels by the number of watts per channel.

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If you have more than one amp you will need to add up the total power figures to get the final total.

STEP 2. Once you have the final total amps you will need to double your number and then divided by 13.8.

The number you end up with is the system’s approximate maximum current draw. With this number and the length of cable that you will need to get from the battery to the stereo.

STEP 3. This easy chart can help to find the wire needed to have the correct power delivered from the battery to your stereo.

The Formula on How to Find What Gauge Wire for the Amp? Gauge Wire Chart

If you get your amperes figured out correctly by doing the math we explained about this should be an easy thing to figure out.

So often doing a little math can save you having to rewire a stereo that is not performing correctly because it has the wrong wiring power.

Cable Gauge Chart

As you can see from the chart you just need to know the length of feet your power is going to travel and the amperes that are being drawn.

In a vehicle stereo you can see that even with a short distance, the variety of wires used in the 0-4 and 4-7 ranges are quite wide.

Often these are the distances to where the amp will be set up, but if you have a car and the amps have to be in the trunk due to the space issue, suddenly the distance can become a very important factor.

Be sure to accommodate for this and to get the right wires the first time. Nothing is worse than getting it wrong the first time and having them do it all over again. Those mistakes are costly, both in time and money, so measure up, do the math and get it right the first time!

Are Amplifiers Efficient?

Amplifiers do have a drawback, the power that is needed to produce the signal is actually much less than the total power needed to run the amplifier. This is because the amp loses power producing heat and resulting in power lost.

The average analog amplifier can lose about 50% of the power provided to heat production. This is a wasted power usage that must be accounted for in the setting up of your system.

This why in the formula that we double the total amps that we need, to account for the wasted power in the amplifier.

Why Do I Keep Reading About 13.8 Volts?

14.4 is the volts that the alternator produces while the vehicle is running, the battery only has 12 volts if the engine is not running (alternator not running).

This is why you use 13.8 to figure out the power supplied, it is a happy middle to the two power levels that your vehicle actually provides.

Now for all this to actually matter you have to have an alternator that works correctly and a battery that actually takes and holds a charge.

As you add extra high-end components to pull power from the system, you need to be sure to keep an eye on the parts of the electrical system of your vehicle to be sure that they are running at peak condition all the time.

Wire Length?

Wires produce resistance in them to electrical current. So, this means that to deliver the full voltage to the end of the wire the gauge must be large enough so the current when it arrives is useable.

This means if you have to run the wires a long distance, you will need to size up the cables to be sure that the correct voltage arrives at the stereo and amplifiers.

This means that you can actually choke the electrical volts out of your own system with the wrong wire. Be sure you know the needed volts for the equipment you are running, and that your vehicle can provide these volts based on the electrical system and the wiring you use.

Wire Gauge Matters

Gauge is the measurement to show the thickness of the wires you are using. This means that larger the gauge, the physically thicker the wire.

The confusing part is the bigger gauge is listed with a smaller number, for an example, the 2-gauge wire is much thicker when 10, 12, 14, or 18-gauge wire. This gauge helps to figure out the ability of the wire to deliver electrical current down the length of the wire from one component to the next.

The simple diagram from the top really shows how the gauges number gets bigger, but the wire size actually gets smaller.

This can be confusing and pretty much everyone at some time gets this turned around and has come home with the wrong wire size because they remembered it the other way around.

So, run the numbers and be sure you know the gauge of wire that you need before you go out and spend that hard earned cash. No one likes having to go back to the hardware store over and over!

Speaker Wiring Matters Too

Speaker wires again need to be of a sufficient size to deliver the signal and power that the speaker needs to operate properly.

From the initial delivery of power, all the way to the speaker that produces the sound we listen to the wire size must be correct, so the system can operate properly.

You need to understand the length of wire you need, use a string to run from the amplifier to the speakers. This will give you a very close idea of how much wire you will use.

Be sure to use the wires that the speaker calls for, and only adjust if you must. And the even better solution is to get speakers that come with the wires included.

This can save the difficulty of having to figure out what is right and then be having to source the wire yourself.

How Do You Know What Size Fuse To Use?

Each car stereo, amplifier, and speaker set will come with built-in fuse systems.

These are factory systems and the fuses in the components should only be replaced with proper fuses to be sure nothing gets damaged for being overpowered or even underpowered.

As you have power delivered from the battery to the entire system you do need to use a fuse to protect the system form possible power surges. This means you need to use a fuse that is not less than 14.4 volts that the alternator on the vehicle provides.

You do not want the music to cut out just because the fuse blows under normal operating conditions. The main fuse needs to be as close to the battery as possible, and that means often they are on the main wire and very close to the battery post.

The fuse needs to be able to handle the amps that are drawn from the main power supply. If you had two amplifiers and they each run at 40 amps, you would use an 80-amp fuse.

Getting the right fuse is again a case of simple math and research. Your owner’s manual should list the draw for each of the components that you have installed in your vehicle audio system.

If you do the calculations and do not come up with a matching fuse size, always pick the next size bigger. If you find that you are blowing fuses to often you will want to get a multimeter and check the levels in your system as there could be a short or another issue.

When picking a fuse, you can pick barrel fuses, blade fuses, and wafer fuse.

The fuse type that you use will depend on the capacity of the current and your personal choice.

Just be sure that whatever fuse you pick, you can get replacements for it, as the fuse is designed to break when it does its job you will need replacements.

The Pay Off For Getting This Right

Imagine you are driving around town, and your favorite music is flowing loud and clear. You are the one that everyone is looking at because you are bringing the party and riding on the nicest ride around.

The stereo can make or break the vehicle, so be sure that you make it! Often times you see people with fantastic cars or trucks and all they have to listen to are factory stereos, how lame is that?

I mean, your mother listens to a factory stereo. Set yourself apart from the rest of the crowd, but go one step further. You can actually tell peoples that you send up, installed and build this system yourself!

Armed with the information in the article above, you will be the expert. So that your time, get the best components and do the math!

Get your system set up and rumbling loud and clear for all to hear. That is one sure fire way to turn heads and get noticed while rounding down the streets of your town.

Hey, there mobile audio lovers! My name is Vincent Talbot, founder and chief editor at 99carstereo.com. Ask any mobile audio fanatic, installer, or company rep what makes a good car speaker, sub, or amp, or, better yet, why he or she prefers a certain brand over another, and be prepared to endure a litany of opinions, viewpoints, and passion-fueled perspectives. To be honest, mobile audio shopping can be a daunting task without a guide, so I’ve assembled what I feel are the best products to consider to make things easier for you. More.

Why you should trust me?

Mobile audio is my passion, so before I put anything in front of you I exhaustively research a broad range of products, review all the available information on them and ultimately make a curated list of recommendations. As a result, I want this site to be a trusted resource that you can rely on and that is not rigged by brand sponsorship, so you can use this information when you are planning your new mobile audio upgrade.