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Curious Ruler

By Curious Hat

This app is only available on the App Store for iOS devices.


2014 Children's Technology Review Editor's Choice for Excellence in Design

Measure and compare objects around you!

With Curious Ruler, children can explore and measure objects around them and learn about sizes, units of measure, and proportions. 
Curious Ruler is both a useful utility and a great educational tool that supports Measurement and Data Core Standards.

* Simply pick a known reference object in Curious Ruler, like a coin or a sheet of paper, then select an object you’d like to measure.
* Place these objects side-by-side and take a picture.
* Curious Ruler provides sliders to measure the objects and compares their relative sizes.
* Switch between the US and Metric measurement system.

Did you know that the iPad 3 is as long as 27 pennies?
With the Curious Ruler you do!
The interaction is limitless, fun and educational.

The app is designed for ages 3-8.
No external links.
No In App purchases.
No Social Sharing.

42 Reference objects to choose from including:
- US and World coins and paper bills
- iPhone and iPad
- Credit Card
- Crayon
- Lego and Duplo bricks
- US and A4 paper sheets
- soccer, tennis, basket, baseball, golf, football balls
- soda can

Please note that a bug in iOS 7.0.1 causes text not to be displayed correctly.
Affected users should upgrade their iOS to a more recent version.

About Curious Hat
Curious Hat is the world’s leading developer of innovative family application for iOS. Played by children and their parents around the world, Curious Hat apps have raised the design bar for playful, educational apps at home and in school. For more information about Curious Hat and its portfolio of apps, visit

What's New in Version 1.2

Curious Ruler speaks Spanish too!
You can use UK currency as reference objects now!
There are now 42 reference objects to pick from.


iPhone Screenshot 1
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iPad Screenshot 1
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Customer Reviews

Difficult to Use

This app is extremely difficult to use. The app doesn’t let the user see if the items they are comparing are actually straight or lined up with each other until it is too late and the user has taken a picture. It is very difficult to accurately measure the objects. This activity could be completed much more easily without using an iPad or this app, so the app does not actually make anything easier for the user. It does, however, allow students to learn about measurement through non-standard units which is helpful for younger elementary students. Other than that, there is not much else it has to offer.

Curious Ruler
View in iTunes
This app is designed for both iPhone and iPad
  • $0.99
  • Category: Education
  • Updated:
  • Version: 1.2
  • Size: 5.6 MB
  • Languages: English, French, Italian, Spanish
  • Seller:
Rated 4+
  • Made for Ages 6–8

Compatibility: Requires iOS 6.0 or later. Compatible with iPhone, iPad, and iPod touch.

Customer Ratings

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