What Size Amp Do I Need for My Car?

You’re driving along and suddenly your car starts making a strange noise. You pull over to the side of the road and pop the hood, and you see that the engine is smoking. You’ve blown a fuse, and you need to replace it. But what size amp do you need for your car?

You can find out by following these simple steps.

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You finally have all the right components for your car stereo system. Your research has paid off and you have quality speakers, subs and an excellent head unit. But something is missing. The final piece to the puzzle is an amplifier. You know you need one, but what size do you need? Will a small amp work or do you need a large one?

The answer to those questions depends on a few factors such as the power of your speakers, the number of speakers, and how loud you want your system to be. In this article, we will help you understand how much power your speakers need and how to select an amplifier that will give them the juice they need without breaking the bank.

How to pick the right size amplifier

To figure out what size amplifier you need, you’ll need to know two things: the impedance of your subwoofers and the power handling capability of your subwoofers. The impedance of your subwoofers is measured in ohms. The power handling capability of your subwoofers is measured in watts.

Consider the RMS power rating

When you’re looking at the RMS power rating, you need to ensure that the figure given is continuous power and not peak power. Many companies will advertise their amplifier’s peak power output, which can be as much as four times the RMS output. While this may be fine for short bursts of high volume, it’s not what you’re looking for in an amplifier for your car stereo. You want something that will provide a consistent level of power delivery.

As a rule of thumb, you should look for an amplifier that produces around 50 watts RMS per channel. This should be enough to give you a decent level of volume without causing any issues with distortion. If you have a particularly powerful set of speakers or subwoofers, then you may want to consider an amplifier with a higher power output. However, it’s always better to err on the side of caution. It’s much easier to add more amplifiers later on if you need more power than it is to try and tame an amplifier that’s too powerful for your set-up.

Consider the peak power rating

At the very least, you want an amp that can put out as much power as your speakers can handle. This is called the RMS (root mean square) power rating. To find this number, look for the “per channel” or “PC” RMS power rating. This will usually be listed in watts.

You should also consider the peak power rating of your amplifier. This is the maximum amount of power that the amplifier can produce for a very short period of time. It’s important to know this number because it will affect how loud your music can get. The peak power rating is usually listed in watts as well, but sometimes it’s listed in dollars per hour or some other unit of measure.

If you have any questions about which size amplifier is right for your car, consult a professional audio installer or talk to a salesperson at a car audio store.

Consider the impedance

The first thing you need to know is the impedance of your car speakers. Impedance is measured in ohms and is usually either 4, 8 or 16 ohms. Most car speakers are either 4 or 8 ohms. If you have more than one speaker on your amp, then you need to add up all the impedance of each speaker to get the total impedance. For example, if you have two 8 ohm speakers, then the total impedance would be 16 ohms.

Knowing the impedance of your car speakers is important because that’s what will determine the wattage output of your amplifier. The general rule of thumb is that you want an amplifier that can deliver at least twice the power of your speaker’s nominal power rating (measured in watts). So, if you have a pair of 50 watt RMS speakers, then you would want an amplifier that can deliver at least 100 watts RMS to each speaker.


After careful consideration of the make and model of your car, as well as the wattage and number of speakers you’re planning to use, you should have a good idea of what size amp you need. Don’t forget to factor in the space you have available for installation, as well as your budget. With so many options on the market, it’s easy to find an amp that will give you the power you need without breaking the bank.