<p>I want to create parts for a 3D printer using OpenSCAD. Having some STL files from the vendor, but nothing else (no technical drawing, no CAD files).</p>

<p>Does anybody knows a free tool, that allows me to</p>

<ul>
<li>measure distances between 2 selected vertices,</li>
<li>measure distances between a selected vertex and a plane defined by 3 vertices,</li>
<li>measure the radio of a circle defined by 3 selected vertices?</li>
</ul>

<p>I very much like the way Blender allows to work with meshes, especially select vertices or planes, but unfortunately haven't found a way to measure with Blender.</p>

[{'answer_id': 3306, 'author': 'Gunslinger', 'author_id': 5395, 'author_profile': 'https://3dprinting.stackexchange.com/users/5395', 'pm_score': 5, 'selected': True, 'text': '<p>I suggest Blender. It\'s not the simplest of tools but it is free and learning it will improve your 3D printing skills. :-) (I write this answer also for future viewers of this question so I start basic).</p>\n<p>Another answer can be found here, <a href="https://blender.stackexchange.com/q/19772/14005">How do I measure a distance between two points?</a></p>\n<ol>\n<li>Import your STL file.</li>\n<li>Press the Home key to view everything.</li>\n<li>Select the model by clicking on it with your left mouse button. (Blender changed to left-click-select as of version 2.80)</li>\n<li>Hit tab to enter edit-mode.</li>\n<li>Press N (or use View | Properties) until the Properties panel shows up.</li>\n<li>Select the &quot;Length&quot; checkbox in the &quot;Edge Info&quot; section of the Properties panel (see image below).</li>\n<li>Select &quot;Edge Select&quot; mode (see image below)</li>\n<li>Select the edge to measure by clicking on it with your right mouse button.</li>\n</ol>\n<p><a href="https://i.stack.imgur.com/9Oi1c.png" rel="nofollow noreferrer" title="Edge length"><img src="https://i.stack.imgur.com/9Oi1c.png" alt="Edge length" title="Edge length" /></a></p>\n<p><a href="https://i.stack.imgur.com/Ouw0q.png" rel="nofollow noreferrer" title="Screenshot of toolbar"><img src="https://i.stack.imgur.com/Ouw0q.png" alt="Screenshot of toolbar" title="Screenshot of toolbar" /></a></p>\n<p>If you need to measure the distance between to vertices with no edge. Create the edge by selecting them and pressing <kbd>F</kbd>.\nIf you need to measure the distance between a vertex and any other point, select it and press <kbd>E</kbd> to extrude.</p>\n'}, {'answer_id': 14590, 'author': 'Joel Coehoorn', 'author_id': 12562, 'author_profile': 'https://3dprinting.stackexchange.com/users/12562', 'pm_score': 1, 'selected': False, 'text': "<p>If you're running Windows, MS 3D Builder has a measuring tool and may already be installed on your machine.</p>\n"}, {'answer_id': 14592, 'author': 'FarO', 'author_id': 2338, 'author_profile': 'https://3dprinting.stackexchange.com/users/2338', 'pm_score': 1, 'selected': False, 'text': '<p><a href="https://www.meshmixer.com/" rel="nofollow noreferrer">Meshmixer</a> has various measuring tools for STLs as well</p>\n'}, {'answer_id': 16701, 'author': 'Karl Zeilhofer', 'author_id': 29272, 'author_profile': 'https://3dprinting.stackexchange.com/users/29272', 'pm_score': 2, 'selected': False, 'text': '<p>As @Gunslinger suggested, I would also recommend Blender for these tasks.</p>\n<p>Blender comes with the Add-on &quot;MeasureIt&quot;, which has to be activated manually in <strong>Edit ► Preferences ► Add-ons ► Official/Community ►</strong> search for MeasureIt, check the checkbox:</p>\n<p><a href="https://i.stack.imgur.com/qoy5y.png" rel="nofollow noreferrer" title="Blender preferences"><img src="https://i.stack.imgur.com/qoy5y.png" alt="Blender preferences" title="Blender preferences" /></a></p>\n<p>Import your STL file via <strong>File ► Import ► STL ►</strong> ...</p>\n<p>Select your object and hit <kbd>TAB</kbd> to enter Edit Mode and then follow the tips in this screenshot:</p>\n<p><a href="https://i.stack.imgur.com/JmKQz.png" rel="nofollow noreferrer" title="Screenshot"><img src="https://i.stack.imgur.com/JmKQz.png" alt="Screenshot" title="Screenshot" /></a></p>\n'}, {'answer_id': 20173, 'author': 'Baldee', 'author_id': 34954, 'author_profile': 'https://3dprinting.stackexchange.com/users/34954', 'pm_score': 0, 'selected': False, 'text': '<p>Use Meshy &quot;...a WebGL-based tool that does measurements and simple transformations on STL and OBJ files.&quot;: <a href="https://0x00019913.github.io/meshy/" rel="nofollow noreferrer">https://0x00019913.github.io/meshy/</a></p>\n'}]
['https://3dprinting.stackexchange.com/questions/3302', 'https://3dprinting.stackexchange.com', 'https://3dprinting.stackexchange.com/users/5223/']