# Ruler measurement does not give the result that I expect

**URL:** <https://discourse.slicer.org/t/ruler-measurement-does-not-give-the-result-that-i-expect/6484>\
**Category:** Support\
**Created:** [April 11, 2019, 10:23pm UTC](https://discourse.slicer.org/t/ruler-measurement-does-not-give-the-result-that-i-expect/6484 "2019-04-11T22:23:35Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![arcus](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/arcus/32/3434_2.png) [@arcus](https://discourse.slicer.org/u/arcus)\
**Post date:** [April 11, 2019, 10:23pm UTC](https://discourse.slicer.org/t/ruler-measurement-does-not-give-the-result-that-i-expect/6484/1 "2019-04-11T22:23:35Z")

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Hello, I have been using slicer and am comfortable with a few of the modules. When I use the measuring tool (ruler) point to point, on an area that know would be approximately 1mm in length, it shows a number of :55.5? I have the ruler set to measure at mm increments. What am I doing wrong?

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**Author:** ![pieper](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/pieper/32/8_2.png) [@pieper](https://discourse.slicer.org/u/pieper)\
**Post date:** [April 12, 2019, 11:40am UTC](https://discourse.slicer.org/t/ruler-measurement-does-not-give-the-result-that-i-expect/6484/2 "2019-04-12T11:40:12Z")

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Hi -

What kind of data are you measuring? If it’s from something like a jpg or tiff file, then you need to set the pixel spacing so that the measurement tools are calibrated. You can do this in the [Volumes module](https://www.slicer.org/wiki/Documentation/4.10/Modules/Volumes#Panels_and_their_use).

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**Author:** ![arcus](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/arcus/32/3434_2.png) [@arcus](https://discourse.slicer.org/u/arcus)\
**Post date:** [April 12, 2019, 3:42pm UTC](https://discourse.slicer.org/t/ruler-measurement-does-not-give-the-result-that-i-expect/6484/3 "2019-04-12T15:42:58Z")

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It’s an nrrd file. Thanks. I’ll check the volumes module.

Steve