Headphone Jacks and Plugs: 3.5mm, 2.5mm, and Balanced

What the plug numbers on a listing mean

The millimeter number in a wired headphone listing names the diameter of the plug, not the length of the cable. A 3.5mm plug is the common size for portable audio. It fits the headphone jack on many phones, laptops, tablets, and portable players. The 2.5mm plug is a smaller size that appears on some headsets and on some cables for in-ear monitors. The 6.35mm plug, also called the quarter-inch plug, is the larger size used on audio interfaces, mixers, and DJ equipment.

When a listing states 3.5mm, 2.5mm, or 6.35mm, read it as the size of the metal plug at the end of the cable. The same headphone model can appear in more than one plug configuration, so the listing is the place to confirm which end your device needs. For a first pair, the wired headphone guides list models by their stated connection details.

TRS and TRRS: what the letters mean

TRS stands for tip, ring, sleeve, the three metal sections of a plug separated by insulating bands. A plain stereo headphone plug is normally TRS. The tip and the ring carry the left and right audio channels, and the sleeve is the ground connection.

TRRS stands for tip, ring, ring, sleeve, four sections in total. The extra ring carries a microphone signal. That is why headsets with a microphone often use a TRRS plug while plain headphones use TRS. The difference matters when you connect a headset to a device that expects a headphone plug or the reverse, because the contacts do not line up the same way.

A listing may state 3-pole or 4-pole, or it may name TRS and TRRS directly. Either way, the words tell you whether the cable carries a microphone channel. For the cable jack type that appears on different models, see the cable jack type article.

Balanced connections: what they require

Balanced is a connection scheme, not a plug size. In a balanced audio connection, each channel uses two signal conductors plus a shared ground. The word appears on some studio headphones, some premium wired headphones, and on amplifiers designed for them. A balanced cable requires a source device with a balanced output.

Balanced outputs are more common on dedicated headphone amplifiers, audio interfaces, and studio equipment than on phones, laptops, and portable players. If a listing names a balanced cable or a balanced plug such as 2.5mm balanced, 4.4mm, or XLR, check the maker's page for the connection your source offers. For the difference between balanced and single-ended wiring, see balanced vs unbalanced cables.

Which device uses which plug

Phones, tablets, and laptops with a headphone jack use the 3.5mm size. Audio interfaces, mixers, and many DJ controllers use the 6.35mm size. Some high-end portable players and amplifiers add balanced outputs in 2.5mm, 4.4mm, or XLR form. The listing for the headphone and the product page for the device should both state the plug or jack size.

For a wireless headphone, the cable question mostly disappears. A wireless pair connects over Bluetooth, and some models include a 3.5mm input on the earcup for wired listening. Check the listing for a stated input or cable. The wired versus wireless comparison covers when a cable still matters, and the wireless headphone guide lists pairs by their stated battery figures.

What to check before buying a wired pair

Compare the plug size on the listing with the jack on the device you plan to use. If the plug is 6.35mm and your laptop has a 3.5mm jack, you need an adapter or a cable that ends in 3.5mm. If the listing does not mention an adapter, plan to add one or pick a model whose cable ends in the size you need.

Check whether the cable is detachable. A detachable cable lets you replace it or swap to a different plug size without replacing the headphone. Read the maker's page for the cable connection type and for whether spare cables are sold. The detachable cable guide explains what to look for in the listing, and the closed-back guide is a good starting point for studio use.

Adapters and label words

The words 3.5mm to 6.35mm adapter, 6.35mm to 3.5mm adapter, or included adapter on a listing describe how the plug size changes. A 3.5mm plug with an adapter becomes a 6.35mm plug at the tip. An adapter changes the physical fit, not the signal wiring.

A listing that says 3-pole means a plain stereo plug. A listing that says 4-pole means the plug carries a microphone channel as well. Some listings also state TRRS or 4-pole for headsets. When a listing gives none of these words, read the maker's page for the connection details before you buy. For USB-C versus 3.5mm questions, see the USB-C versus 3.5mm article.

What to pick for your situation

Questions

What does 3.5mm mean on a headphone listing?

It is the diameter of the plug at the end of the cable, measured in millimeters. 3.5mm is the common size for headphone jacks on phones, laptops, tablets, and portable players.

Is a 2.5mm plug the same as a 3.5mm plug?

No. 2.5mm is a smaller plug diameter. It appears on some headsets and on some balanced cables. A 2.5mm plug does not fit a 3.5mm jack without an adapter.

What is a TRRS plug?

TRRS stands for tip, ring, ring, sleeve. It has four contact sections. The extra section carries a microphone channel, which is why headsets with a microphone use TRRS plugs.

Do wireless headphones have headphone jacks?

Some do. A wireless pair may include a 3.5mm input on the earcup for wired listening. The listing states the input size when it is present.

What is a balanced cable?

A balanced cable uses two signal conductors per channel plus a shared ground. It requires a source device with a balanced output, such as a dedicated headphone amplifier. A standard 3.5mm or 6.35mm jack is not a balanced output.

Do I need a balanced connection?

Only if your source device offers a balanced output and the headphone listing names a balanced cable or plug. A regular headphone jack works with any wired headphone that fits it. Compare wired models in the best wired headphone guide.