Reducing square duct to round duct

I have a square duct of 20* 20 mm outer dimension whitch I want to reduce to a round duct of 10 mm outer diameter via a kind of elbow bend. Both ducts have a wall thickness of 1 mm. Is it possible to do this by means of the extrusion tool, follow me tool or else way?

Rather a common question. Try this thread:


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I manged to make the reducer from a square duct to circle duct as shown in the picture. Thank you for the information.
My original idea was to make the reducer with a round curved elbow bend. is this possible?

There are several ways to do that depending on the shape you want.
Here is a quick one using Fredo’s Curviloft.


DIt works perfect, thanks

SketchUp First Try
@Box Hey I know this is an old thread but I got jammed up on an square to round fitting for my HVAC models and your advice was the hot ticket. Had to play with the Fredo Curviloft origin points until I got it right but I can’t tell you how much time you saved me…if I would have been even able to do it at all with native tools so I thank you my friend.

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You can do HVAC modeling quickly, easy and fun with my free plugin VBO Ducting Basic. Please give this a test


I don’t do ducts really, but WOW that plugin looks cool!

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