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Does a true 3/8″ ID hose still have 1/4″ fittings?

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Does a true 3/8″ ID hose still have 1/4″ fittings? Or are the fittings 3/8″ also, asks Mike B.?


If it is a hose, and it’s 3/8″ in size, it will have a hole size 3/8″ in diameter. The outer hose diameter will vary depending on the make and quality.

You can install any fitting desired into the 3/8″ hose by using adapters as necessary.

Rubber Air Hose
Rubber Air Hose

If it is a 3/8″ tube, then the O.D. of the tube will be 3/8″, and the hole size in the middle correspondingly smaller.

If the question is what is the hole size in the fittings on a 3/8″ hose, the answer again will depend on the hose manufacturer and quality. A 3/8″ hose that comes with a fitting on either end should reasonably have 3/8″ holes for optimum air flow, but don’t bet on it. See the size chart on the NPT fitting page on this site for a guide.


“Does a true 3/8″ ID hose still have 1/4″ fittings?” Mike b asked. Typically, yes. But you can get 3/8, says Doug from s.d.ca.

Trouble is, it won’t fit much anything else, unless you put 3/8 fittings on the “else”. Some Makita tools, for instance, can use 3/8. (The else being the connector for the air tool, etc. – moderator)

““Or are the fittings 3/8″ also?” A half-inch hose might come with 3/8 or 1/2 fittings.

In any case, a 3/8 hose will of necessity, have a smaller than 3/8 connector, because it has to fit inside the hose. Typical barb connectors have about an inch of 1/4 bore, then flare out to a shade under 3/8, in 1/4 pipe size, which is about 1/2 across.

I know, confusing, ain’t it?

Try going to a hardware store and look at some fittings, pipe, and tube. Compare the stated size with an actual measurement with a tape or ruler.

And a historical note: old pipe was cast. !/4 inch cast pipe has/had a 1/4 bore, but is about 1/2 diameter due to wall thickness. New, drawn or extruded pipe has a thinner wall, so the ID is near 3/8.

And do take a look at the charts Bill mentioned.

Have fun, Doug.


When air tank and air hose has pressure in them, should it be hard to connect and disconnect a tool or tire gage from the quick connect on the hose? adds Mike B.


Yes indeed. The charge of air will make it quite a bit harder to disconnect a tool from the connector, and when it comes apart, expect a large (relatively speaking) burst of air as the downstream air vents back up the connector.

You can acquire couplings that can be vented before disconnecting should the pressurized disconnection process be an issue for you. Good luck.

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By Bill Wade

About Air Compressors has been helping folks with their Air Compressor Problems since 2002 online. We're a community of DIY and Compressed Air professionals who are keen to support everyone across the globe with their air compressor issues and troubleshooting. Whether you're trying to identify an old air compressor, or troubleshoot an error code on a sophisticated new industrial air compressor - the community at About-Air-Compressors.com is here to help you

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