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App review by Debbie Gorrell, Common Sense Education | Updated February 2015
Curious Ruler

Curious Ruler

Measuring app inspires curiosity; limited to a reference tool

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Based on 1 review
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Subjects & Skills

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1 video | 5 images

Pros: Fun, interactive tool teaches early measurement skills.

Cons: Kids can't apply or assess what they learned.

Bottom Line: The app is worth a try if you're looking for a way to get kids interested in measurement.

Use Curious Ruler as a fun introduction to a measurement unit. Have kids work in pairs to measure several sets of objects. Depending on their age range, you could put together a box of objects for kids to measure, or you could have them look around the classroom to find objects. Come together as a class and discuss the results. Then ask kids to try to visually compare three objects. For example, ask kids to guess how much longer or shorter a pencil is than a sheet of paper and a yardstick.  

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Curious Ruler is an interactive tool kids can use to compare the lengths of two objects. They start by choosing one of 36 reference objects -- from different coins and bills to DVDs and legal paper. Then they choose an object to measure and place both objects side by side within the camera's view. Kids tap anywhere on the screen to take a photograph, and then drag sliding rulers on the next screen to measure both objects. The measuring tool displays either metric or U.S. units, and general comparisons of the lengths of the two objects. It also displays a comparison of the measured object to a handful of other reference objects. Please note that iOS 7 causes problems with text display, so the developer recommends that users update their iOS to a more recent version.

Kids can learn how to measure and compare the lengths of two objects. These are important early concepts for kids to grasp, and it helps build their visual-spatial skills and estimation strategies. One feature allows users to express the lengths of the two objects in either the metric or the U.S. system. The other feature focuses on comparison. For example, when kids choose a golf ball as the reference object and a permanent marker as the object to be measured, the results show that the marker is 3.1 times longer than the golf ball. This feature in particular does a good job of addressing an early Common Core standard. Some activities to apply and/or assess learning could help improve the learning value of Curious Ruler.

Overall Rating


Kids will like snapping photographs of objects, and comparing them is fun for a while. Some additional activities could boost engagement.


Teaching kids how to visually compare the lengths of two objects is important, as is measuring the objects with actual units. It would be great to see a way for kids to apply or assess learning.


The simple design makes navigation a snap, and a video tutorial can be found on the developer's website.

Common Sense reviewer
Debbie Gorrell Educator

Community Rating

Featured review by
Crissy W. , Classroom teacher
Classroom teacher
Village of Barboursville Elementary School
Barboursville, United States
A tool to introduce measurement
This is an app that is free and useful for an introduction to measuring. It can be used fairly easily by the students independently after given instructions on how to use it. Therefore, it could be used easily for a center as well. It does not go very in-depth with measurement - just covers the basics.
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