Math Open Reference

Visually plain, no-frills collection of math simulations

Learning rating

Community rating

Based on 3 reviews

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Expert evaluation by Common Sense



Subjects & Skills

Critical Thinking, Math

Price: Free
Platforms: Web

Pros: Interactive content wrapped in a simple package still delivers with tight, clear wording and digestible math chunks.

Cons: Ads can annoy and confusingly lead to other math sites.

Bottom Line: Free collection of math interactives and geometry construction tutorials.

Teachers can use Math Open Reference to easily project and step through constructions with the whole class. Next, students re-create them using the site until they are eventually able to do it with real drawing tools. Of course, when homework time rolls around, kids can peek back at the site if memory fails. Function explorers provide concrete illustrations of linear equations and more. Try letting students play with the sliders and see how changing different variables transforms the shape of the graph.

Math Open Reference is a free interactive math reference covering high school geometry, functions, and calculus. Five organizing topics cover plane, coordinate, and solid geometry, plus trigonometry and calculus. A few function explorers and a general online scientific calculator arm kids with tools that help them visualize what all these numbers and formulas actually mean.

Most entries open with a definition, follow with concise explanations of relevant concepts, and then end with links to other relevant topics. Embedded "Try This" activities invite kids to interact with dynamic diagrams by moving intersecting points, lines, or vertices and watching the results. A large number of entries are actually constructions -- step-by-step animations showing kids exactly how to find the "center of a circle using any right-handed object," for example.

Math Open Reference has some hidden gems despite its plain package and often confusing sidebar ads for other math sites. Concise, accurate explanations provide a solid foundation for a series of dynamic construction and manipulation applets that pull kids into the experience and build deeper, concrete understanding of geometry concepts. The constructions in particular show kids through animated protractors and pencils (and downloadable worksheets) how to bisect an angle, divide a line segment into equal parts, or draw a parallel line through a point.

While site owner John Page calls it a textbook in his mission statement, the terms reference and construction guide are more precise. Other sites featuring math simulations such as Desmos provide formative assessments that teachers can monitor; exercises with immediate feedback and a teacher dashboard are missing from Math Open Reference. Also missing is standards alignment, though many of the simulations align to the Common Core Math Standards.   

Learning Rating

Overall Rating

Missing real-world context or games to make math interesting. The site isn't visually appealing, but easy to navigate.


Concepts are well defined with clear language. The applets and "function explorers" provide visual representations of math concepts.


Content is offered in all of the languages offered through Google Translate, including Esperanto, Haitian Creole, and Basque. Additional opportunities to extend student knowledge are needed.

Common Sense reviewer

Community Rating

Look past the simple appearance and you can find a great geometry tool.

This has the potential to be an absolutely wonderful tool. It is not there yet. The website is an interactive geometry text book. Originally designed for high school, it is easily used in lower grades to introduce a wide variety of topics. You have to be careful to avoid the ads that look like they are part of the site. There can be a lot of them. I also got one about how to improve your abs. While possibly helpful in its own way, not helpful during a classroom introduction on angles. The great part is that for a topic, you will get an interactive model, key vocabulary with definitions, demonstrations, possible extension ideas, and related topics. The interactive models, in my opinion, are the biggest asset of this website. They will give students visual models of the topics that they can move around and see how the vocabulary is related. For example, when introducing angles, the model lets you move around the angle and will give you the exact measurement as well as the type of angle (acute, obtuse, right...) as you move it. If they can get rid of the ads, or make them more appropriate, this could be a wonderful teaching tool that would be available to the students anywhere that they can get online.

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