How To Measure Car Speakers And Subwoofer Size

Hi, I’m Joe, and I was on a recent trip to Laguna Beach in my friend’s car. Oh Man, what a bass and power those car speakers had. I loved it!

So I thought about replacing the existing car speakers in my car with a new one.

But for that, I should first know how to measure car speakers’ size cause different types of car speakers are there and the replacement speakers should rightly fit in the car speaker cabinet.

how to measure car speakers

I’m already aware of how to get this done but are you? If not, I’ll help you. I will share some easy methods to measure the size of the car speakers for easy installation.

  1. Mounting Bracket Diameter
  2. Cutout Diameter
  3. Speaker Driver Size
  4. Speaker Mounting Depth
  5. Speaker Mounting Screws Diameter

So, without further delay, let’s dive into the topic. Come along with me!

Just a small note:

Before we get into the actual process, you have to check two things:

  • First, see if the speaker cabinet has a recessed angle. 
  • Next, check the speaker’s depth (of the existing ones) so that the components of the car speaker you wish to buy will fit in the cabinet. 

The 1st step is crucial. If the speaker cabinet has that recessed bevel cut into it, then you will need only 2 measurements to measure the speaker’s diameter.

But if not, please ensure that the speaker’s baffle cutout diameter is smaller than the cabinet’s diameter.

I’ll explain these terms inside the content, don’t worry!

Now that the initial steps are done, let’s see the actual process. Below, I have described some dimensions that are important for car speakers. 

But before that, you first need to unscrew the mounting bracket of the speaker with a flathead screwdriver.

car speaker mounting bracket

See the image above to see what the mounting bracket in a speaker looks like.

If the speaker system in your car isn’t a factory-installed setup, you will find that the speakers are mounted with screws only.

Now depending on the type of screw threads, choose the appropriate screwdriver.  

I got the right one! Fine, now remove all the screws. 


  • Only if you are sure you can unscrew the mounting bracket safely do it by yourself; otherwise please ask the help of a technician so that you don’t damage the speaker.
  • Also, disconnect the car battery before doing the unscrewing part. This will help you to prevent any unprecedented shocks.

After the initial step is done, you need to take some measurements. They are as follows.

1. Diameter of the mounting bracket:

  • Take a measuring tape in your hand and drag it over the center of your car speaker.
Diameter of the mounting bracket

Can you see the picture above, the same way, make sure the tape’s hook is fixed onto one edge and the other edge should be moved over to the mounting bracket’s other edge. Now you will get the overall diameter of the mounting bracket.

  • If your existing car speakers don’t have any mounting brackets, don’t worry. Just measure the outer diameter of your car speaker. Find an apt mounting bracket before installing your car speaker to achieve the perfect fit.

2. Speaker’s baffle cutout diameter

I don’t want to confuse you with the technical definition of baffle cutout diameter. Do you see the picture before, this is exactly what the speaker’s baffle cutout diameter is.

Why is the Cutout diameter of a car speaker critical?

This is an important measurement that plays an important role in positioning the speaker inside the mounting hole of the speaker cabinet.

I would always recommend the cutout diameter be smaller than the mounting hole. I say so because you will face installation problems due to the tight fit if it’s the opposite case.

How To Measure Car Speaker’s Cutout Diameter?

  • First, flip the speaker upside down such that the magnet is on the top of the speaker.
  • Take the measuring tape/ruler in your hand and hold it on the top of the speaker driver, as shown in the figure.
  • Now look from the top of the magnet down and hook one side of the measuring tape over the edge where the speaker cone starts and drag the tape across to the opposite side. This will give you your speaker’s cutout diameter.

3. How to measure car Speaker Driver Size

Measuring the Speaker driver size and the mounting depth is more or less the same way. You can understand it by following the picture given in the following topic.

4. How to measure car Speaker Mounting Depth

This measurement will tell you much space you will need behind your speaker so that no contact happens between the magnets or other objects.

Generally, the mounting depth will be greater for home use top-mount speakers.

But for car speakers, you should be careful with this. If the speakers have a deep mounting depth, you will have installation problems.

How to Measure Speaker Mounting Depth?

  • Turn your speaker over on its side, such as the speaker’s cone facing up.

Measure the distance from the top of the speaker mounting frame to the flat bottom surface with a measuring tape.

Note: I recommend that the new speakers you get are not higher than the existing speakers. Only then will you have no problems with installation or issues caused by the touch of the magnets.

speaker measurements

5. Mounting Height

Now, what is this Mounting height, let’s see. Mounting depth tells you how much space you need behind the speaker right.

Mounting height on the other hand will tell you how far the speaker’s front will protrude out of the door panel after installation.

6. How to measure speaker Mounting Screws Diameter

Measuring the diameter of the screw is pretty straightforward (Use a tape measure or a ruler) and the easiest measurement you can take. So I’m not explaining that, but let me tell you why this measurement is important.

If you go wrong with this measurement, the speakers will fit correctly in the cabinet, but one of the screws will be outside the rings’ outer diameter, which will not look nice.


In this article, I explained how you have to measure the car speaker’s size. These measurements will be really handy when you replace the existing one with a new set of car speakers.

Most speakers have the dimensions noted at the back of the box. But if you don’t find them, then you must make a note of these measurements.

Apart from the steps above, you may also need to measure the speaker mounting holes, like their diameter and height. But that’s very simple. You need to place a ruler over the mounting to get the dia and place the ruler inside the mounting hole as far as it goes inside to determine the height of the mounting hole.


1. What measurement do you need while installing a speaker or subwoofers?

  • Diameter of the speaker mounting bracket.
  • Baffle cutout diameter or speaker cutout diameter.
  • Car speaker driver size.
  • Car speaker mounting depth.
  • Car speaker mounting height.
  • Distance between parallel mount screws.


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