How to Measure Speakers


8" Garage Bagger Speaker

Speaker Sizes Over the Years

The first speakers that were commercially available to the general public began to appear over one hundred years ago in the form of household radios.  These radios were extremely basic compared to the sound systems of today, but at the time, they were cutting edge technology, and every household in America wanted one.  Various styles and sizes of radios began to appear as manufacturers increased their available models and as other manufacturers started producing their own version of what a radio or speaker should be.  

One of the biggest game changers in the advancement of speaker technology and popularity was the arrival of car stereo systems.  Home audio equipment was often stationary due to its size.  Early radios and speakers were often housed in large wooden boxes that resembled a piece of brown furniture, and they often blended in so well that they were used as tables.  The parts making up home radios were large because they didn’t particularly need to be small, but putting speakers into a vehicle required the use of smaller equipment because interior space was at a premium. 

Advances in battery technology allowed radios and speakers to become small and portable, and nowadays high quality speakers are even found in cell phones.  Automotive speakers have been produced in various sizes over the years, but have always been limited in size due to the need to fit smoothly and uniformly into a vehicle’s interior, and manufacturers used the same size speakers to save on costs.  It was a lot easier for car companies to use parts that were interchangeable with other models, and even other brands, so a few popular sizes became the universal industry standard for a long time. 

Automotive Speakers

Almost every vehicle produced over the last half-century has come standard with a radio or some sort of audio head unit, and multiple speakers located in the dash or on the interior door panels.  The speakers vary in size based on make and model but are usually one of a dozen or so industry standard-sized speakers.  Sound system upgrades are one of the most popular upgrades for vehicles, so extra speakers are often added, and stock speakers are often upgraded due to failure, or just because higher quality speakers with better sound quality are required to get the desired results.  Stock speakers can usually be purchased directly from automotive manufacturers, but many aftermarket stereo systems companies produce higher quality speakers that are a direct replacement for the original.

Replacing stock speakers with updated and better examples is a straightforward process that can be accomplished by anyone with a little bit of mechanical knowledge with a basic tool set.  While the brand and quality of the speaker will be a personal choice for each individual, the size of the new speaker will be determined by the size of the previously installed speaker.  Finding out what size speakers you will need is an easy and straightforward process, and following these steps will give you the information you need to measure and find the right fit for you.

Steps to Measure Your Speaker

The process of finding the right size replacement speaker starts with measuring the speakers that are currently installed, and this can be broken down into several simple steps, including removing the speaker, measuring the diameter of the speaker, measuring the cutout diameter and the mounting holes, and measuring the speaker height. 

Remove the Speaker

The first step of measuring a speaker is removing it from its housing and this is often the most complex and time-consuming step of speaker measurement.  You will first want to disconnect the battery or power source for safety reasons, and then you can start removing parts.  Some automotive speakers are easy to remove, those found in door panels and rear shelves, and some dashes will sometimes only require the removal of four screws, but others can require specific manufacturer information, so if the removal process isn’t obvious, further research might be required. 

Usually a speaker assembly is attached to what it is housed in using several Phillips head screws, which are easily removed, allowing you to pull the speaker forward and out far enough to disconnect any wires or electrical connectors that send signals to the speaker.  While every speaker’s removal might not be this simple, it will have to be removed to take accurate measurements to find a suitable replacement.

Measuring the Diameter

Now that the speaker is removed, it is time to find out the speaker’s size, and the first step is finding the speaker’s diameter.  The diameter is found by taking a tape measure, ruler, or yardstick and measuring the speaker at its widest point across its face (or front).  It is important to write down this number and all subsequent information as soon as it is measured to save you from forgetting and having to repeat any measurements. 

This is an easy process if the speaker that is going to be replaced is round in shape, but many speakers feature an oblong shape, and newer model cars can even feature custom shapes.  If this is the case with your speakers, and they are not round,  other measurements will need to be made.  If this is the case, then you will need to measure the widest point from each side and record these as well to be sure your replacement is a perfect match.

Measuring the Cutout diameter and the Mounting Holes        

Once you have the speakers’ physical diameter and size, you will want to inspect the hole it was removed from and measure its diameter as well.  The hole that the speaker fits into is usually smaller than the diameter of the speaker it houses, this is due to the speaker having an outer lip with holes for mounting screws that is wider than the rest of the speakers housing or baffle.  This outer lip allows the speaker to fit firmly against whatever it is housed in, and these mountings can be either flush against the housing or slightly recessed for a more secure fit.

Another important thing to look at when measuring a speaker is to take note of how many mounting screw holes the speaker has, and where they are located on the speaker.  Measuring the distance between screw holes will allow you to match up a replacement perfectly.  There might be a chance that a replacement speaker will not have holes that match the original exactly, or the screw hole sizes might be too small on the replacement, but as long as you have the proper measurements, new holes can be drilled.  

Measuring Speaker Height

The height or depth of a speaker is the last important measurement that will have to be taken in order to be sure you are getting the correct replacement speakers.  The height can be found by placing the speaker on its side and measuring the distance between to front and back of the speaker.  Finding the height is extremely important because while externally a speaker might look exactly the same from the front, and visually looks like a suitable replacement, the housing might not have the depth to accommodate the new speaker.  This can often be an issue in cars and trucks, and especially boats and motorcycles, where space is at a premium, so measuring a speaker’s height is an important part of the process. 

Why Is it Important to Have the Correct Speaker Size

So why exactly is it so important to measure your speakers to be sure you have the correct speaker size?  It all comes down to being sure you can source an exact replacement for your original speaker.  In today’s world, there are more speaker options and sizes than ever before, and finding a replacement can be confusing, so the more knowledge you have (like precise speaker measurements) beforehand, the easier it will be to find a replacement.  If a replacement speaker is too small, it will never fit right, and if it’s too big, then in-depth time-consuming non-reversible modifications will need to be made.  Knowing exactly which size speaker you need will streamline your speaker replacement process and allow you to complete your speaker upgrade quickly. 

Once you have the proper speaker measurements, where is the best place to search for a replacement speaker for your automobile, boat or motorcycle?  Look no further than Garage Bagger Stereo.

Update Your Speakers at Garage Bagger

Once you have measured your old speakers and are ready to purchase upgrades, things can get confusing.  There are plenty of cheaply made speakers for sale online, but Garage Gagger Stereo carries the best brands in the business.  Garage Bagger Stereo specializes in marine grade audio equipment and speakers for boats and motorcycles that are subject to prolonged exposure to the elements, so the products they carry are engineered to operate at peak performance in harsh conditions.  Boat and motorcycle stereo systems also have to deal with space constraint issues that other sound systems don’t have to deal with, so the folks at Garage Bagger are experts when it comes to using speaker measurements to get a perfect fit.  No matter what your project is, big or small, they can help you come up with the equipment you need to accomplish your goals.

If it’s time to update and upgrade your speakers, then Garage Bagger Stereo is your one-stop shop for the best brands and equipment on the market, and  if you have any questions, they are just a phone call or email away.  So measure your speakers, head over to , order your perfect-fit replacements, install them, and enjoy many future hours of listening to your favorite tunes!

This Blog Was Reviewed for Accuracy By Audio Expert, Chris Lowe

Chris Lowe, the esteemed owner of Garage Bagger Stereo, is a globally recognized authority in Motorcycle and Boat Audio systems. With a decorated experience spanning over a decade, Chris has curated audio experiences for enthusiasts and businesses worldwide. His expertise and stellar work are prominently showcased across various social media platforms and can be further explored through the offerings on the official Garage Bagger Stereo website.

Originally hailing from South Georgia and currently residing in Greenville, South Carolina, Chris's fervor for boating and motorcycles is deeply rooted. It's this passion, coupled with his affection for car audio, that has seamlessly interwoven his personal interests with his professional pursuits. This synergy has not only invigorated his daily endeavors but also continually fuels his commitment to excellence in the audio industry.