DIN is a standard that was created by the German standards body Deutsches Institut für Normung ("DIN"). The standard specifies a height and width for car head units. When a unit is referred to as a single DIN car stereo, or a single DIN car radio, that means it is the height and width outlined in the DIN standard.
Automakers and car stereo manufacturers around the world use this standard, which is why most head units are interchangeable. While the wiring is not standardized, the DIN standard is the reason why you can replace OEM car stereos with aftermarket devices.
Although the DIN standard only specifies a single height and width, head unit manufacturers also produce devices that are twice as tall. These double-tall units are referred to as double-DIN since they are twice the height of the single-DIN standard. A small number of head units are 1.5 times the height of the DIN standard, which technically makes them 1.5 DIN.
How Do You Tell If Your Car Radio Is Single DIN?
The easiest way to tell if a car radio is single DIN is to measure it. If the radio is about two inches tall, it's probably a single DIN. If it's roughly four inches tall, then it's double DIN. A 1.5 DIN radio, which is somewhat rare, will fall in between those measurements. There are no other standardized DIN measurements.
Some vehicles are trickier than others. For instance, if a dash has three vertically stacked slots that are all about two inches high, and only one is taken up by an OEM radio, then it's probably just a regular single DIN head unit. In such cases, it is difficult to tell if a larger head unit can be accommodated.
In most cases, consoles with gaps above or below a single DIN head unit were originally designed to house a CD player or another piece of audio equipment. Some car dealers may have original factory equipment laying around that can be installed in such a situation.
Replacing a Single DIN Car Radio
When you're ready to replace your single din car radio, the easiest option is to buy a single DIN aftermarket unit. While there are sometimes slight differences in fit and finish, most single DIN aftermarket units are designed to be installed in an adjustable collar that facilitates installation in just about any single DIN slot.
Replacing a Single DIN Radio With Double DIN
Since double DIN head units are twice the height of single DIN head units, you can always go from double to single, but the reverse may be a challenge.
Before attempting such an upgrade, it's important to first measure the "slots" and verify that they can be accessed. The additional slot should be two inches tall. Some vehicles have "dummy" slots that look like they're designed to accept a device like a CD player but are intended for storage. Such an opening may fit a 1.5 DIN unit, or it may be too small. You may also find that there is no removable cover, and even if you removed the housing there could be a mess of wires or ducting that prevent the installation of a double DIN head unit.
Dash Space and Other Difficulties
Assuming your console has space, the next problem you'll run into is the wiring. Even if you're trying to replace a single DIN head unit with a double DIN head unit, you'll typically find that the wiring harness connectors aren't the same. That means you'll either have to find an adapter or use a wiring diagram to splice a new connector into your existing wiring harness.
The next issue you may encounter is that even if your console has a blank slot underneath the head unit, it may be molded into the dash. Even if it is removable, it's not likely to fit anything more than a single DIN device like a CD player. If you want to replace your single DIN head unit with a double DIN device, you may have to cut out the part of the dash that separates the two slots.
If your vehicle had the option for a double DIN head unit, then you may be able to replace your existing dash or center console bezel with one that's designed for a double DIN head unit.
Why Double DIN?
Before you go through all the work to replace your single-DIN radio with a double DIN head unit, ask yourself if it's worth it. Although double DIN head units have a lot more real estate for features like touchscreens and internal space for features like more powerful amps and built-in CD changers, those expenses add up quickly.
If you're looking for a big touchscreen, you can find single DIN head units with slide-out screens. You can also add components like an external amplifier or CD changer without cutting into your dash bezel, and you may even be able to use that additional single DIN slot for a graphic equalizer or some other useful audio component.