How to measure car speakers

How to measure car speakers

Johann a TV mounting Technician and Editor
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5 min read for expertise

Last Updated on May 23, 2022 by Johann Holsinger

Making the choice to replace your car’s factory speakers with aftermarket speakers is something millions of people do.

However, the DIY upgrade can be a somewhat confusing and potentially frustrating process if you dont know the details or what size speaker to get.

You need to find a specific size of the speaker that will fit in the same place as the factory speaker unless you make custom modifications and build custom speaker mounting spots.

First, you need to know “how do you measure a car speaker?”

Installed car speakers on the trunk

The importance of getting the right size of car speakers

Getting the right size speaker not only ensures that the speaker can fit into the existing space you have in mind but also sounds better when you’re driving around and blasting your favorite tunes.

Your speaker won’t become loose and start to rattle from the vibrations if the old hole is too big.

Knowing how to measure car speaker diameter correctly is the best first step to making sure you will have a pleasant and easy time when installing your new aftermarket car speakers.

Installed car speakers on the door

So that you get a new speaker of the same size as what was previously installed or ready for your upgrade.

Get new speakers that fit the same mounting hole in your car, and are the same circumference as your old speakers.

Speaker quality and output potential have nothing to do with the speaker’s size.

Make sure the wattage of the new speaker matches your head unit

When learning how to measure car speaker size, having a suitable match between your speakers and the head unit is important for making sure the speakers are not undersized in terms of wattage.

Having higher wattage speakers than what your head unit will give will present the best sound and avoid the potential of speaker damage.

If your speakers are too powerful, your head unit can be severely damaged.

If your head unit is much more powerful than your speakers, the sound quality can be heavily distorted.

Do most car speakers have a standard size?

While you can find a standard range of speaker sizes, there is no specific standard size.

Even speakers that share the same standard range can be slightly off on precise measurements or hole alignment.

This varies between manufacturers because a speaker size has to be compatible with the car’s design [1].

The wrong size can make mixing and matching different speakers difficult at times, so we reccomend getting speakers that are the right size for an easy replacement and upgrade.

Car speakers close up

What sizes are you looking for in a car speaker?

1. Cutout diameter

The first measurement of speaker size you should take is to know the cutout diameter. The cutout diameter is the measurement of the widest part of the cone which will snug fit in the mounting hole.

The most common cutout diameter is a 4-inch diameter round hole, as well as a 6×9 oval.

Your cutout diameter will be smaller than the diameter measurement of the speaker itself.

Cutout diameter and mounting depth

2. Mounting screws diameter

The mounting screw’s diameter is the measurement of the distance between screw corners.

Most factory-installed speakers will have a 3-hole screw placement.

However, aftermarket speakers will normally have a 4-hole placement.

Diameter measurement will be listed on the specifications of your chosen speakers.

Mounting screw diameter of a speaker

3. Mounting height

The mounting height is the distance from the speaker’s external panel to the bottom of the speaker.

Many speakers have a mounting height of 0.5 while your vehicle may only have 0.25. In this case, you can install a spacer ring to give you the extra room needed.

4. Mounting depth

When measuring the mounting depth, you want to be sure you have enough clearance between the magnet and the surface of the mounting frame.

If the magnet is obstructed, sound can be affected.

What sizes are you looking for in the mounting hole?

1. Outer diameter

If you have no idea what to measure for a car speaker hole, start with the outer diameter.

The outer diameter is normally the measurement of the speaker itself. For example, if you purchased a 4” speaker, the outer diameter will be 4 inches.

2. Inner diameter

When measuring for the inner diameter, do not take into account the flange or mounting bracket as these will sit on top of the area you are mounting the speaker to.

A closer look of a mounting hole's inner and outer diameter

3. Inner depth space

Ensure you provide the speakers with enough inner depth space for the magnet and cone, as well as the tweeter on the front to be unobstructed by paneling or the speaker grille.

4. Screw pattern

While not as important as some other measurements, knowing your screw pattern and distance can prevent the need for making additional screw or bolt holes when installing the aftermarket speaker.

How do you measure the screw pattern of the car speaker?

There are four common screw patterns with aftermarket speakers including 4-hole, 4-hole fully flange, 3-hole, and multi-hole.

When measuring for a 4-hole and 4-hole full flange pattern, the measurement will be done diagonally from each screw center.

On 3-hole and multi-hole patterns, measure the diameter entirely and go to the outside edge.

Different screw patterns of car speakers

How do you measure the car speaker’s cutout diameter?

When searching for the entire cutout diameter on a round speaker, you want to measure the speaker to the widest part of its mounting frame or flange [2].

If you have an oval or oblong speaker, measure across the horizontal and vertical axis at the widest points of each.

Car speaker on bare car door

Tips for mounting car speakers bigger than your existing hole

  • Use a rotary tool or Dremel to enlarge the hole in the door or dash to account for the larger speaker cone or mounting frame.
  • Use an adaptive flange to support the mounting frame and internal cone and as a way to reinforce the larger hole you made.
  • Ensure the magnet is not being pressed against any surfaces in the door or dash with internal components.
  • Some vehicles may require heavy modification to make room for larger speakers than what was factory installed.

If you’re looking to install a speaker on the wall, here’s our installation guide for you.

Removing speaker on a mounting hole

Tools needed

  • Philips and flat-head screwdrivers
  • Ruler or tape measure
  • Wire cutters or box cutter
  • Allen wrenches for some factory bolt removal
  • Electrical tape or crimping tool
  • Wire stripper or soldering iron
  • Possibly a Dremel for modifications.

Tools for measuring car speaker size

What is the ideal mounting height and depth?

When choosing a replacement speaker, you want to ensure the mounting depth sees the magnet free from touching any internal components of the door or dash.

For the mounting height, you want to ensure the tweeter and speaker grille is not being pushed into another part of the vehicle when a door is closed, for example.

How do you measure the mounting hole’s outer diameter?

Take your ruler or tape measurer and measure the distance across the speaker’s widest point.

If this is a round speaker you will only need one measurement, but for oval speakers, you will need to measure both horizontally and vertically.

Close up look of a mounting hole's outer diameter with speaker attached

How do you measure the mounting hole’s inner diameter?

Measure in the same way you did for the outer diameter.

Only instead of going all the way to the edge of the speaker, stop before you get to the mounting frame or gasket that may be found.

Pulled out speaker from a mounting hole

Putting everything together: What is the right speaker size for your car?

While every car and truck will have unique requirements, and every person may have specific preferences.

Finding the right speaker for your car will depend on what factory speakers you removed, as well as how many DIY modifications you may want to do when installing a new aftermarket speaker in its place. 

Don’t forget about a subwoofer and a massage chair inside your car.

Check this guide for making a subwoofer box and see you in the next one!

Different car speaker sizes

More information:

  1. Understanding car speaker sizes. a blog from
  2. How to measure speaker size? a guide from

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Johann Holsinger portrait

Hi, my name is Johann Holsinger, here at I share all of the tips and tricks I have professionally learned to help you set up your ultimate home entertainment system.