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I've got this question from one of my best students. The question is the following:

Suppose, that we have Edit mode with some edges, vertices, etc. How to set a selected edge to have a specific length? Numerically?

We already know, that scaling with enabled 'Show edge length' is helpful, but in general, it seems to be easier to just select an edge, and to set its length. This is extremely useful for architecture modeling.

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A quick and dirty way is to type in the number like this "{target_length} / {current_length}". For example, if you want to scale the length of an edge from 1.176 to 4, you can switch the Transformation mode to Normal, then press SEnter, type in 4/1.176 for a certain axis, then press Enter.

P.S.: It won't be accurate since the Mesh Display is not so accurate. You need a small script or addon to get the easier and more accurate calculation. I suggest to use the integrated Ruler/Protractor tool. It can save an numeral value with 8 decimal places if you copy (CtrlC) it. (Tip: The snap feature for the ruler only works well with Wireframe mode, currently.)

There is also another question that collects some good ways to do so. How to get selected edges length?

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  • $\begingroup$ Your post makes no sense if you don't explain how to navigate through the menu. I was unable to follow this. $\endgroup$ – Krythic May 8 '16 at 2:16
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This feature is now in an included addon in Blender 2.79 called Mesh: Edit Tools 2. You have to enable the addon in the User Preferences.

User Preferences...

  1. Go to Add-ons
  2. Search "edit"
  3. Click the box for Mesh: Edit Tools 2
  4. Save User Settings

Enable Mesh: Edit Tools 2

While in Edit Mode, press W for the Specials Menu

  • Edit Tools > Set Edge Length
  • Input a target length and click OK.Resize Edge

Hope this helps! I searched forever to find the answer. Shoutout to Danyang Yi for providing the link to a previous version of this addon prior to it being included in Blender.

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It's seems you guys will like this addon.

enter image description here

Toolbar > Tools > Mesh Tools > edges set.

  • Set Length: ShiftAltE
  • Set Angle CtrlShiftAltE
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One way to set the length of an edge is:

  • Select the edge in edit mode
  • Scale to size 1 SNumpad /current edge lengthEnter
  • Scale again to the desired length in blender units say 2.5 S2.5Enter

An easier way would be to extrude the edges from a single vertext from the start.

  • Select vertext (Edit mode; vertext select)
  • EX,Y or Zdesired lengthEnter

For architecture modelling there is also an addon called archimesh.

Other related questions:

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Clunky and bait for floating point shenanigans.. but it works:

  • From N menu, show Edge Length.
  • In Edit Mode using vertex select, choose the vertex you want to keep where it is, then move 3D cursor to it (ShiftS, 4)
  • In edge select mode, select the edge
  • Hit main keyboard (not numpad) Full Stop/Period (.) to set 3D cursor as scale/rotate pivot
  • Hit S, type the current length of the edge and hit / then Enter - this will scale it to 1 unit exactly (/ toggles whether the scale amount entered is inverse)
  • Hit S again, type the length you want the edge to be in Blender units and hit Enter
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I've needed to create a trapezoid with top edge 50 cm and bottom 100 cm.

The easiest way I've found is to: 1. create a "Helper" plane mesh 2. (Press N to show the right panel if not seen.) in the Transform section under Dimensions set it's desire axis to the exact length. In my case I've set the Y axis to be 50cm. 3. Select the real object (your mesh) and enter edit mode (Tab). 4. At the bottom panel toggle "Magnet" on and choose "Vertex" and "Closest". 5. Now drag (G) the desired vertex to the "Helper" object. The magnet will make sure you do it correctly. After you dragged the 2 vertexes to the correct "Helper" vertexes exit edit mode. 6. Repeat from step 2- in my case I changed it's size to 100 cm and then adjusted the relevant bottom vertexes.

Hope this help, If not say so And I can maybe upload instructions with pictures

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