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I know in most CAD programs, you when you have a ruler/measurement tool, you can just click the measurement, type in a number, and the segment will resize (and if you lock proportions, the entire object will scale so that the segment fits the size). I have no clue how to do this with Inkscape 1.1.

Resize segments to specific length

I want to set the shape so that the side segments are exactly 10 mm. How do I do this?

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    There might be some smart way to do this, but the most hands on way would be to simply scale the object to 10 / 10.13 of its current size. Besides that, this method for Illustrator/InDesign might be possible to adapt to Inkscape, or you could calculate how tall a dodecagon should be for its segments to be 10 mm and then scale to that height.
    – Wolff
    Sep 26 at 11:39
  • @Wolff - sorry I think I stole your idea. LOL
    – Billy Kerr
    Sep 26 at 14:41
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    @BillyKerr, no worries. I could've just posted an answer. Ideas in comments are up for grabs, aren't they? 😀
    – Wolff
    Sep 26 at 15:40
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You can measure a segment with the Measurement tool - essentially a ruler - which is at the bottom of the toolbox. Of course, you can also access it using it's keyboard shortcut, the M key. Enable snapping, and snap to cusp nodes. Click and drag to measure the segment.

enter image description here

Divide the segment length you want to scale it to by the measured segment length, and multiply that by one hundred to calculate the percentage for the scale.

Using my example above, that would be 10/45.24×100 = 22.1043324%.

Then do a Scale Transform using that percentage - that should get you very close to the desired size.

Example, showing measurement after scaling (zoomed in a bit):

enter image description here

However, note that Inkscape is not designed for CAD drawings/plans - it's graphics software used for creating SVGs, not for engineering/architecture, and lacks the mathematical precision that CAD tools offer.

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  • You say that Inkscape lacks the precision of most CAD programs; are there any open-sourced CAD programs that are compatible with SVG files?
    – Donna V.
    Sep 27 at 1:03
  • @DonnaV. I've no idea. Sorry. I do graphic design, so I don't use CAD software. Inkscape is for making pretty graphics, not for technical/CAD work. Maybe google it: "open source CAD software".
    – Billy Kerr
    Sep 27 at 10:19
  • I suppose for the purpose of graphic design, it really doesn't matter if things are a 1/10th of a millimetre off. Bit of a shame though that SVG files don't have any sort of macro for absolute figures that are calculated by approximated by the specific computer displaying them e.g. if as a point, you could have in the XML code (1, sin(pi/4)), and the computer does the rest so that you have it as precise as the computer wants.
    – Donna V.
    Sep 27 at 22:40
  • @DonnaV - yeah, also note that for ellipses or arcs, you will often find these have been converted to SVG paths which use Bézier curves, which can only approximate those. Also SVG = scalable vector graphics. The format itself was developed for browsers to render graphics, a kind of XML, somewhat similar to HTML - essentially plain text files. Big numbers in the XML would increase the file size, which is not ideal for use on the web. SVGs are often optimised for the web by reducing the number of decimal places.
    – Billy Kerr
    Sep 28 at 8:22
  • @DonnaV. The problem isnt SVG the problem is that you are looking for a indirect modeller and inkscape is a direct modeller with some indirect functions. You think that all CAD applications are indirect modellers but that is not true. Some are direct indeed. THing is though, indirect modellers work in reverse to how a direct modeller works, so having used a indirect modeller you think upside down for a direct modeller. There are some pros and some cons with each approach. Direct modellers are easier to operate up front but harder to operate once your goal changes.
    – joojaa
    Oct 13 at 8:46

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