Curious Ruler




Interactive measuring is briefly fun but needs more depth.

What parents need to know

Ease of play

It's pretty easy to snap the photographs, but figuring out how to drag the correct rulers to measure each object and how to take photographs of multiple sets of objects is a bit challenging. 

Violence & scariness
Not applicable
Sexy stuff
Not applicable
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Drinking, drugs, & smoking
Not applicable

Parents Need to Know

Parents need to know that Curious Ruler is an interactive tool that kids can use to compare measurements. There are built-in reference objects from which kids choose a starting point. Then, they find another object to use as a comparison and snap a picture of both objects, side by side. The tool will tell kids how long the chosen object is compared to the reference object. It's fun to play around with, and kids will enjoy taking pictures of different objects, but don't expect to get a lot of learning value. Measurements cannot be saved, and the option to switch units is confusing and does not produce any significant information. 

What kids can learn



  • measurement


Thinking & Reasoning

  • collecting data
  • part-whole relationships

Engagement, Approach, Support


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

Learning Approach

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.


A simple design makes navigation fairly easy, and a video tutorial can be found on the developer's website. 

What kids can learn



  • measurement


Thinking & Reasoning

  • collecting data
  • part-whole relationships

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. Some activities to apply or to assess learning could help improve the educational value of Curious Ruler.

This Learning Rating review was written by Debbie Gorrell

What's it about?

Kids 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 they drag sliding rulers on the next screen to measure both objects. The measuring tool will display a general comparison of the lengths of the two objects. It also will display a comparison of the measured object to a handful of other reference objects.

Is it any good?


CURIOUS RULER is an interesting way to expose kids to early measurement skills. Kids will like taking photographs of objects, and the visual comparison of two lengths is a great way to build visual-spatial skills. However, there's not a lot of depth to the learning experience. Without actual units displayed, kids will not be able to apply what they learn to other situations. And, without the ability to save measurements or to assess what they've learned, kids likely will not remember much of the experience.   

Families can talk about...

  • Families can talk about how measurements and comparisons are used in everyday life. When do we need to measure things, and what types of things do we need to measure?

  • Use rulers with different units to measure the objects and compare the results to the app's results. Encourage kids to do the math to find out if the comparisons are accurate.

  • Go on a scavenger hunt to find fun things to measure. 

App details

Devices:iPhone, iPod Touch, iPad
Pricing structure:Free
Release date:May 8, 2014
Size:6.90 MB
Publisher:Curious Hat
Minimum software requirements:iOS 6.0 or later

This review of Curious Ruler was written by

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Learning ratings

  • Best: Really engaging; great learning approach.
  • Very Good: Engaging; good learning approach.
  • Good: Pretty engaging; good learning approach.
  • Fair: Somewhat engaging; OK learning approach.
  • Not for Learning: Not recommended for learning.
  • Not for Kids: Not age-appropriate for kids; not recommended for learning.

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