Headphone jack sizes come in three common diameters: 2.5 mm, 3.5 mm and 6.35 mm. The diameter decides whether a plug fits a socket. The number of metal sections on the plug decides what it carries: mono sound, stereo sound, or stereo sound plus a microphone.
This guide covers both. The connector facts come from Wikipedia’s article on the phone connector, and the questions come from two Reddit threads. EARSOLE has not measured or tested any plug or adapter for this article.
Key takeaways
- There are three common plug diameters: 6.35 mm, 3.5 mm and 2.5 mm.
- Wikipedia describes 3.5 mm plugs as nearly universal for portable audio equipment and headphones.
- Count the metal sections on the plug: two is mono, three is stereo, four usually adds a microphone.
- When an adapter misbehaves, forum replies suggest checking how firmly the plug is seated, then the cable.
The three headphone jack sizes
Wikipedia lists three sleeve diameters for this connector family.
| Diameter | Inch value | Name Wikipedia uses |
|---|---|---|
| 6.35 mm | 1/4 inch | Full-sized |
| 3.5 mm | 1/8 inch | Mini |
| 2.5 mm | 1/10 inch | Sub-mini |
The inch values for the two smaller sizes are approximations. The three sizes are the same kind of connector at different diameters, so a plug of one size needs an adapter to fit a socket of another.
What is a 3.5mm headphone jack?
It is the mini size in the table above. According to Wikipedia, the 3.5 mm size was originally designed in the 1950s as a two-conductor connector for earpieces on transistor radios. The three-conductor version became very popular with the Walkman in 1979.
What is the standard headphone jack size?
There are three common sizes rather than one standard, and each has its own territory. Wikipedia says 6.35 mm plugs are common on home and professional audio equipment, while 3.5 mm plugs are nearly universal for portable audio equipment and headphones. It describes 2.5 mm plugs as not as common.
For phones and laptops, the same article says the 3.5 mm size became standard on mobile phones. Wikipedia notes that a four-conductor 3.5 mm plug is used on some laptop computers and most mobile phones.
What is a 6.35 mm headphone jack?
It is the full-sized version, often written as 1/4 inch. A 3.5 mm plug will not fit a 6.35 mm socket without an adapter, and a 6.35 mm plug will not fit a 3.5 mm socket without one either.
What is a headphone jack called?
It has several names. Wikipedia lists audio jack, headphone jack, stereo plug, microphone jack and aux input as names for the same connector family, depending on what it is used for. The 3.5 mm size is also called a mini jack.
How to tell which size you have
Measure across the metal shaft of the plug and compare the result with the three diameters in the table. The sizes are far enough apart that an ordinary ruler is enough to tell them apart.
If you have no ruler, use a plug you already know. Since 3.5 mm plugs are nearly universal on portable audio equipment, the plug on an ordinary pair of wired earbuds makes a reasonable reference. If it seats fully in your device’s socket, that socket is most likely 3.5 mm as well. This is a rule of thumb, not a measurement.
Counting the metal sections: TS, TRS and TRRS
Diameter is only half the answer. Wikipedia explains that plugs are also named by their number of contacts:
- TS has 2 contacts and carries mono audio.
- TRS has 3 contacts and carries stereo audio.
- TRRS has 4 contacts, typically for a stereo headset with a mono microphone.
You can count them on the plug itself. Each metal section is one contact, and the sections are separated by thin insulating bands.
There is one caveat for four-contact plugs. Wikipedia’s USB-C article says there is no agreement on which TRRS rings carry ground and which carry the microphone, so devices with a headset jack and microphone input must be able to swap them. That is one reason a headset microphone can behave differently from one device to another.
Does a bigger jack sound better?
A poster on r/headphones had a cable with both plugs and asked: “If I use the 3.5mm will the quality be worse?” A reply in the thread was two words long: “Doesn’t matter.”
That is one commenter’s answer, not a measurement. The evidence gathered for this article contains no measured comparison between plug sizes, so treat it as a forum opinion.
Adapters between sizes
Adapters are where the complaints come from. A poster on r/HeadphoneAdvice wrote that with several 3.5 mm to 6.35 mm adapters, “turning the cable in the adapter causes the audio quality to drop/change”.
The replies suggested three things to check:
- The seating. One commenter asked whether the plug was pushed all the way in.
- The cable. Another commenter thought the cable itself might be broken.
- The socket. The same commenter wondered whether the 3.5 mm jack had a bad connection.
That second commenter also brought up the number of contacts, but only for the reverse arrangement. In that case, they wrote, a simple TRS adapter with TRRS headphones would cause this kind of problem. For the poster’s own setup they could not think of a way the adapter could be responsible unless it was a TRRS one.
These are suggestions from individual commenters, and the replies read for this article do not confirm which one was the cause.
What the EARSOLE wired listings say
Two EARSOLE wired products state their plug in the listing.
The White 3.5 mm Wired Earbuds listing describes soft in-ear tips and a straight 3.5 mm plug, and says the cable connection suits devices with a compatible headphone output.
The Black Wired Headphones with Inline Control listing describes a folding design with an inline control and a right-angle 3.5 mm plug.
Neither listing states how many contacts the plug has, and the headphones listing does not say whether the inline control includes a microphone. Before ordering either one, check that your device has a 3.5 mm headphone output.
What this guide does not cover
It covers the three diameters in Wikipedia’s summary. Other plug sizes exist and are left out. The connector facts are an encyclopedia summary, and the forum material is a handful of individual replies.
What is the standard headphone jack size?
There are three common sizes: 6.35 mm, 3.5 mm and 2.5 mm. Wikipedia describes 3.5 mm plugs as nearly universal for portable audio equipment and headphones.
What is a headphone jack called?
Wikipedia lists audio jack, headphone jack, stereo plug, microphone jack and aux input as names for the same connector family. The 3.5 mm size is also called a mini jack.
Is a 6.35 mm headphone jack better than 3.5 mm?
A commenter on r/headphones answered that it does not matter. That is a forum opinion, not a measurement.
