# Distance measurement

**URL:** <https://discourse.slicer.org/t/distance-measurement/8495>\
**Category:** Feature requests\
**Created:** [September 19, 2019, 10:17am UTC](https://discourse.slicer.org/t/distance-measurement/8495 "2019-09-19T10:17:39Z")\
**Posts on this page:** 9\
**Page:** 1

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**Author:** ![RadioQuest](https://avatars.discourse-cdn.com/v4/letter/r/85f322/32.png) [@RadioQuest](https://discourse.slicer.org/u/RadioQuest)\
**Post date:** [September 19, 2019, 10:17am UTC](https://discourse.slicer.org/t/distance-measurement/8495/1 "2019-09-19T10:17:39Z")

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Hi…  
Is there a tool to measure the distance between 2 points. (ruler annotation is not useful).  
I need some kind of ruler or scale to measure the size/ distance.  
Thanks.

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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:** [September 19, 2019, 12:22pm UTC](https://discourse.slicer.org/t/distance-measurement/8495/2 "2019-09-19T12:22:27Z")

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> [@RadioQuest](#):
>
> ruler annotation is not useful

Annotation ruler can measure distance between two points. Why it is not suitable for what you want to do?

You can drop two markup fiducial points and get the distance between them by going to Markups module, selecting both fiducial points in the list, and right-click in the list.

 ![image](https://us1.discourse-cdn.com/flex002/uploads/slicer/original/3X/a/5/a5e35e25920514647975f597b18ee749656b42f5.png)

We are improving markups on recent Slicer Preview versions, adding a line tool, which is somewhat more convenient (but it does not display the distance value yet, so for now you have to compute it from the point coordinates yourself).

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**Author:** ![RadioQuest](https://avatars.discourse-cdn.com/v4/letter/r/85f322/32.png) [@RadioQuest](https://discourse.slicer.org/u/RadioQuest)\
**Post date:** [September 19, 2019, 12:59pm UTC](https://discourse.slicer.org/t/distance-measurement/8495/3 "2019-09-19T12:59:59Z")

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Yes this works.  
Thanks a lot!

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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:** [September 19, 2019, 1:14pm UTC](https://discourse.slicer.org/t/distance-measurement/8495/4 "2019-09-19T13:14:47Z")

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Great! Why ruler was not suitable? (just asking so that we can take it into consideration when improving markups lines)

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**Author:** ![RadioQuest](https://avatars.discourse-cdn.com/v4/letter/r/85f322/32.png) [@RadioQuest](https://discourse.slicer.org/u/RadioQuest)\
**Post date:** [September 19, 2019, 1:43pm UTC](https://discourse.slicer.org/t/distance-measurement/8495/5 "2019-09-19T13:43:27Z")

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Hi…  
I am trying to measure the distance - for example 2 cm lateral from midline , etc. So I needed a tool that will help me to select my region easily anywhere. Also it would be useful to measure the distance between any two points. This present ruler does not seem to be that useful if I know the distance and place point accordingly.  
please correct me if I am wrong.  
Thanks.

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**Author:** ![anilpawar](https://avatars.discourse-cdn.com/v4/letter/a/cab0a1/32.png) [@anilpawar](https://discourse.slicer.org/u/anilpawar)\
**Post date:** [May 13, 2022, 11:26am UTC](https://discourse.slicer.org/t/distance-measurement/8495/6 "2022-05-13T11:26:08Z")

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Hi, thanks for clear steps to measure the length. Still I am a small query. I am using it for CT images where pixel spacing is in mm. So this measured length will be in mm or pixels unit?

Thanks in advance.

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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:** [May 14, 2022, 8:08pm UTC](https://discourse.slicer.org/t/distance-measurement/8495/7 "2022-05-14T20:08:31Z")

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Measurement is always in physical units (you may not even load an image, but you may measure distances on surface meshes, etc).

Unless you change the default unit in the application settings, the physical length unit is millimeters.

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**Author:** ![anilpawar](https://avatars.discourse-cdn.com/v4/letter/a/cab0a1/32.png) [@anilpawar](https://discourse.slicer.org/u/anilpawar)\
**Post date:** [May 17, 2022, 3:42am UTC](https://discourse.slicer.org/t/distance-measurement/8495/8 "2022-05-17T03:42:37Z")

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Thanks a lot for quick reply and confirmation 🙂

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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:** [March 21, 2023, 2:03am UTC](https://discourse.slicer.org/t/distance-measurement/8495/9 "2023-03-21T02:03:55Z")

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