<h1>.stl Basics</h1>
<p>The .stl format has no inherent sense of which units you use. items are to scale to an ambiguous 1, which could be 1 meter, one millimeter, one lightyear or one inch. To a .stl, only the <em>relative</em> sizing matters. All these faces you see are compared to a line with the length of 1-unit that is</p>
<h1>Slicer-Modeling Software interaction</h1>
<p>The most common graphic design programs export in millimeters, but some US ones just assume inches, which is a factor of 1&quot;=25.4mm.</p>
<p>Cura, Netfabb, and Slic3r expect that the 1-unit line is one <strong>millimeter</strong> long - but if it is an inch instead, then the model is shrunk by 1/25.4 or to about 4% of the right size. Scaling up by 2540% one would return to the millimeter scale.</p>
<p>But then there are other programs that use other choices of scales. <a href="https://blender.stackexchange.com/questions/7503/scale-settings-for-exporting-to-stl-for-3d-printing">Blender</a> for example assumes a scene is in meters by default.</p>
<h1>Inventor</h1>
<p>Inventor can export .stl in a variety of scales, which all just serve as how the length of the inherent but invisible 1-unit line is drawn. The default choice is <strong>centimeters</strong>, so a scaling factor of 1cm=10mm, which would explain the models being only 1/10th of the expected size in Slic3r. to change the scaling, follow the <a href="https://knowledge.autodesk.com/support/inventor-products/learn-explore/caas/CloudHelp/cloudhelp/2014/ENU/Inventor/files/GUID-59FB702C-F37A-4DEA-ADCF-51AD8A219C9B-htm.html" rel="nofollow noreferrer">manual</a>:</p>
<ul>
<li>upon exporting a .stl, click <code>Options</code></li>
<li>under Units, choose <code>mm</code></li>
</ul>

CC BY-SA 4.0
2018-12-02T19:37:20.697Z
From the images he added, the model length and width are in the 100s.
Perplexed Dipole
CC BY-SA 4.0
2018-12-02T19:46:09.323Z
@PerplexedDipole his *other* picture shows about 2 division lines on a prusa bed on an edge that should be 200mm. 20mm instead of 200mm is what factor? 1/10th.
Trish
CC BY-SA 4.0
2018-12-02T09:53:17.977Z
2018-12-02T19:47:14.253Z
2020-06-18T08:29:41.667Z
Trish
<p>I made a few models in Autodesk Inventor. When I tried to get them printed, the printer created a model smaller than the model I made in Inventor (270mm x 200mm). Is there a way to keep them from getting resized?</p>

<p>Here is the model in Inventor:
<img src="https://i.sstatic.net/P7L7L.png" alt="The model in Autodesk Inventor">
And here is the model being visualized by the printer driver:
<img src="https://i.sstatic.net/XtaNN.png" alt="The model being visualized by the printer driver"></p>

CC BY-SA 4.0
2018-12-03T19:23:04.333Z
Luckily, it doesn't matter, since all slicing programs allow you to scale the dimensions.  So long as you know at least one edge-to-edge dimension, you can handle this.
Carl Witthoft
<cad><stl>
How do I keep the .stl files from being resized while exporting?
user3482676
# How do I keep the .stl files from being resized while exporting?

(Asked by: username_0 on 2018-12-01)

I made a few models in Autodesk Inventor. When I tried to get them printed, the printer created a model smaller than the model I made in Inventor (270mm x 200mm). Is there a way to keep them from getting resized?

Here is the model in Inventor:
![The model in Autodesk Inventor](https://i.sstatic.net/P7L7L.png)
And here is the model being visualized by the printer driver:
![The model being visualized by the printer driver](https://i.sstatic.net/XtaNN.png)

**Tags:** cad, stl
> **Comments:**
> **username_1**: Luckily, it doesn't matter, since all slicing programs allow you to scale the dimensions.  So long as you know at least one edge-to-edge dimension, you can handle this.  

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## 1 answers

### Answer by username_2 on 2018-12-02. Score: 3 | Accepted answer

# .stl Basics

The .stl format has no inherent sense of which units you use. items are to scale to an ambiguous 1, which could be 1 meter, one millimeter, one lightyear or one inch. To a .stl, only the *relative* sizing matters. All these faces you see are compared to a line with the length of 1-unit that is

# Slicer-Modeling Software interaction

The most common graphic design programs export in millimeters, but some US ones just assume inches, which is a factor of 1"=25.4mm.

Cura, Netfabb, and Slic3r expect that the 1-unit line is one **millimeter** long - but if it is an inch instead, then the model is shrunk by 1/25.4 or to about 4% of the right size. Scaling up by 2540% one would return to the millimeter scale.

But then there are other programs that use other choices of scales. [Blender](https://blender.stackexchange.com/questions/7503/scale-settings-for-exporting-to-stl-for-3d-printing) for example assumes a scene is in meters by default.

# Inventor

Inventor can export .stl in a variety of scales, which all just serve as how the length of the inherent but invisible 1-unit line is drawn. The default choice is **centimeters**, so a scaling factor of 1cm=10mm, which would explain the models being only 1/10th of the expected size in Slic3r. to change the scaling, follow the [manual](https://knowledge.autodesk.com/support/inventor-products/learn-explore/caas/CloudHelp/cloudhelp/2014/ENU/Inventor/files/GUID-59FB702C-F37A-4DEA-ADCF-51AD8A219C9B-htm.html):

* upon exporting a .stl, click `Options`
* under Units, choose `mm`

> **Comments:**
> **username_3**: From the images he added, the model length and width are in the 100s.  
> **username_2**: @PerplexedDipole his *other* picture shows about 2 division lines on a prusa bed on an edge that should be 200mm. 20mm instead of 200mm is what factor? 1/10th.  

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