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How to Measure Car Speakers Size?

When replacing car speakers, you want to make sure that new speakers have the correct size and will fit in your car.

Most of the speakers have their dimensions written down. However, when this information is missing, you must measure the existing speakers. But how to measure speaker size to ensure it will fit the car? Let’s find out.

To measure the speakers’ size, set the speaker upright, so the widest part of the cone is facing up. Then, use a ruler or tape and measure at the widest point of the speaker from one edge of the mounting frame to the other. If the speakers are not circular but oval, take several measurements around the speakers.

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Tip: Measure all speakers’ dimensions is not too complicated, but it should be done using precise measure tape or a good quality ruler.

I use a transparent ruler, which is especially handy when measuring the screw mounting holes.

However, for measuring depth or speakers’ height, I found it better to use a metal measure tape. My favorite is a CRAFTSMAN tape with a self-lock mechanism.

In the article below, I will go through all critical dimensions that define whether specific speakers will fit into your car. 

What Dimensions Are Important For Car Speakers?

When looking at the speaker, you see at least a dozen different sizes within all shapes. Although all of them are critical from the speakers’ design side, not all are important when thinking about installing them in the car.

Mounting Depth

Mounting depth tells you how much room we need behind a speaker to ensure no contact between the magnet and door panel or any other objects after installation.

When speakers are too deep, you may have a problem with either installation as a whole or with the blocked movement of the door windows.

Mounting Height

Mounting height tells you how far the speaker’s front sticks out of the door panel after installation.

This dimension is critical, especially in the coaxial speakers with tweeters higher than the speaker’s surroundings being mounted behind the door panels.

If you install speakers behind door panels without original speaker grills, it is worth ensuring there is enough free space in front of the speaker after mounting.

Cutout Diameter

The cutout diameter of the speakers directly affects the positioning of the speaker inside the mounting hole. Although the speaker should fit nicely in the hole, there is no room for a tight fit.

It is better to have a cutout diameter slightly smaller than the mounting hole rather than too tight.

A tight fit can cause installation problems and increase the risk of damaging the speaker’s basket. In worse cases, a weaker speaker basket can be distorted and damaged.

Mounting Screws Diameter

The diameter of the mounting screws is essential if you want to ensure a stable speaker location in the mounting hole.

There are slight differences between similar speakers, even if they are theoretically the same. For example, 6.5″ is not always precisely 6.5″. It is, therefore, crucial to know the exact dimension.

In case of differences, you can mount the speaker that will end up being in the offset, or when placing it on top of the MDF distance rings, you can have one of the screws outside of the ring’s outer diameter.

Noteworthy is also the number of the mounting holes you want to measure. For example, when a speaker has four mounting holes, the measurement of these dimensions is straightforward, and the only thing you have to do is measure two holes that are across from each other.

More complicated is to measure car speakers with three mounting holes. In this case, handy will be speakers’ factory specifications and compare it with the speaker we want to purchase.

In some cases, however, installing the speakers on the distance rings will automatically change the number of mounting holes to match the new speakers.

how to measure car speakers

How to Measure Car Speakers Screw Pattern?

Screw pattern is the easiest dimension to be measured with no difference for the round, oval, or square speakers. Use a tape measure or a ruler to measure it correctly, and take your measurements for the speaker holes across from each other.

The more difficult it is to measure the screw pattern in the speakers with a nonsymmetrical shape or uneven mounting holes.

However, these are specific cases, and when replacing such speakers, it is better to use adaptor rings fitting the original location in the car.

Conventional sized aftermarket speakers have a wide choice of different models to choose from, so you can select a speaker to fit your needs.

how to measure car speakers mounting screws diameter

How Do You Measure Speaker Cutout Diameter?

To measure cutout diameter, flip the speaker upside down so the magnet is on the top of the speaker.

The cutout diameter is the widest part of the cone attached to the back of the speaker basket. The right way to measure it is to use the ruler and look from the top of the magnet down.

However, using a ruler may not be the most accurate. More accurate results you will have when using large vernier, which jaws will cover both sides in the widest point of the speaker.

If your speaker is not round, measure the widest point from each direction. Remember that the cutout diameter must be smaller than the mounting hole in which the speaker will be installed.

how to measure speaker cutout diameter in car speakers

How to Measure Speaker Mounting Depth?

To find the mounting depth, you have to flip the speaker again and place it on the flat surface with a cone facing up.

When the speaker lies on its magnet, measure the distance between the flat bottom surface and the bottom of the mounting frame.

Make sure your new speakers are not higher than measured factory speakers, otherwise you may have problems installing them, or it may cause speakers to damage when the magnet touches other metal car elements.

how to measure mounting depth in car speakers

How to Measure Speaker Mounting Height?

To measure speaker mounting height, place the speaker with the cone facing up.

The height of the speaker that stays above the mounting area can be measured using two rulers. Place one ruler horizontally on top of either speaker surrounding or the tweeter in coaxial speakers, ensuring parallel position against the mounting area.

The second ruler place in a vertical position across the top ruler and bottom of the mounting frame. The measurement you take is the distance between both surfaces.

When buying new speakers, make sure they are not too tall that could cause damage when in contact with other objects, like plastic door panels.

How to Measure Speaker Mounting Holes?

The only tool you will need to measure the mounting hole outer diameter is the ruler.

Look at the shape of the hole and determine the widest area. If the hole is round, place a ruler across the mounting hole. For mounting holes with different shapes than round ones, you have to check the widest and smallest diameter and measure both.

Remember that the mounting hole should be slightly bigger than your speaker’s cut-off diameter. Otherwise, the speaker will not fit freely.

How to Measure Depth of the Speaker Mounting Hole?

Mounting hole depth is critical to fit the speaker without the risk of the magnet’s contact with the interior door panel.

To measure it right, place the ruler inside the mounting hole and push it as far back as it can go, and check the value.

When measuring depth, you have to check several points across the diameter and in the center of the hole if the bottom surface of the mounting hole is uneven.

When you have several different measurements from the various points, your maximum depth is the smallest value you have found.

When buying new speakers, make sure their depth is smaller than the minimum measured depth of the mounting hole. Otherwise, the speaker will not sit flat on the mounting surface, or installation may not be possible at all.

Why Car Speakers Have Different Sizes?

Although the manufacturers use standardized sizes, the actual differences between the speakers, even within the same range, which are not higher than a fraction of an inch, or a few millimeters, can disqualify some speakers from installing them in your car.

Many 6.5″ are not exactly 6.5″, or 6×9″ are not 6.9″. That is why knowing which speaker dimensions are important, and you need to know this before purchasing and installing them in your car.

The last thing you want is to install hi-end speakers that make the perfect sounds you need and to find out that it is too deep so you cannot open a window.


When researching the speakers, you need to know several measurements and the manufacturer’s information to determine if the speakers will fit in the car.

The size designation is closely related to their frame’s diagonal measurement and hole alignment. So it’s not just about the diameter of the speaker’s cone or the cutout diameter, which is a common misunderstanding.

Determining the size of the factory speaker in your vehicle can be tricky. These speakers do not always match the aftermarket speakers’ standards because the factory speakers are designed to work with a specific vehicle and have unusual height or magnet depth.

The easiest way to replace car speakers is to buy their direct factory replacement. However, it does not make much sense since we want to improve car audio sound quality and not just replace speakers.