101 question: changing radius of cylinder

Hi folks,

I’m very new to Rhino 3D and have a hopefully simple question. I created a circle and extruded it to create a cylinder. Is there a way to edit the radius/diameter of the cylinder other than Scale2-D? This command works but requires that I enter a scaling factor when what I would prefer is to enter the new radius/diameter directly. In other works, if I want to change a cylinder with a diameter of 1.5" to one with a diameter of 1" the Scale2-D command requires that I enter a scaling factor of 0.666 which is not quite as exact as simply entering the new diameter of 1".


I’d be inclined to just delete the 1.5 and add the 1.0.

Hi Raymond - you can set a radius:

  1. Scale2d
  2. Set the base point at the center of the circle.
  3. Set a first reference point on the circumfernce (i.e. you’ve just defined two points at the end of a radius)
  4. now type the desired radius, and .

Any luck?


Hi pascal,

The number I type is not being read as the new desired radius value but rather the scaling factor. Actually, entering a value of 1—which should result in no scaling at all—changes the diameter of the cylinder from 1.5" to 2.0". Very strange.

Hi Raymond - see if this helps:



I found a workaround by creating a new circle curve at the desired diameter, centering it at the end of the cylinder, then using Scale2-D to transform the cylinder and having it snap to the new curve.

Okay, it works now. The problem seems to be that I used the diameter option when first creating the circle but the Scale2-D is expecting a radius value. Thanks for the help.

One thing to keep in mind with Rhino is the command used to create an object, has nothing to do with editing it later.
To use your example, you drew a circle using it’s diameter option. The resulting circle is no different than one you used the Radius on, or any of the other options.
No parameter value or vestige of using the diameter option is saved with the circle.

Noted. Thanks for the clarification.

Hi Pascal,

Sorry to hijack this thread but I noticed when you went into the Scale command your typed “cen” as your origin. Does typing other OSnaps work and does it work on other commands? I never knew about that trick


Hi Andrew - yes you can always type an OSnap as needed - it lasts for one pick and overrides any set persistent snaps. I did it that way, I think, because my mixed monitors (one high res one normal) makes it hard to get Rhino looking correct on my standard 1024 by 768 capture size, and the Osnap toolbar was way out of proportion and useless…

Cen End Mid Near Knot Perp Tan Quad Point Vertex Int OnSrf OnCrv etc etc.


Awesome thanks! I knew of the right clicking but not typing the OSnap

For a simple shape like a cylinder you could also use box edit to type in the new dimension.

or if you model with _History then you can use _ModifyRadius on the circle and get the extrusion updated accordingly. Yes, that’s Rhino: 10 answers to 1 question -> 101 :wink:

1 Like

BoxEdit is nice. I’ll have to read up on History. Thanks all.

Box Edit would be my tool of choice for this one as well.