# Unit of stl object

**URL:** <https://discourse.slicer.org/t/unit-of-stl-object/26624>\
**Category:** Support\
**Created:** [December 7, 2022, 12:11pm UTC](https://discourse.slicer.org/t/unit-of-stl-object/26624 "2022-12-07T12:11:50Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![yousra](https://avatars.discourse-cdn.com/v4/letter/y/a87d85/32.png) [@yousra](https://discourse.slicer.org/u/yousra)\
**Post date:** [December 7, 2022, 12:11pm UTC](https://discourse.slicer.org/t/unit-of-stl-object/26624/1 "2022-12-07T12:11:50Z")

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how to define the unit in mellimetre on slicer to print the correct dimension of the stl object

thank you

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**Author:** ![lassoan](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/lassoan/32/13_2.png) [@lassoan](https://discourse.slicer.org/u/lassoan)\
**Post date:** [December 7, 2022, 12:39pm UTC](https://discourse.slicer.org/t/unit-of-stl-object/26624/2 "2022-12-07T12:39:38Z")

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Unless you change the sizing scale when you export the STL file, the length unit in the STL file is the same as the length unit in the scene. The length unit in the scene is millimeter by default. All clinical images use millimeter as length unit, too.