University of Illinois at Urbana-Champaign
Office for Mathematics, Science, and Technology Education
College of Education @ University of Illinois

The Online Geoboard

Geoboard example

Instructional animation by Linda Stojanovska

The Concept:

Use the Java Applet of a real Geoboard to construct any number of shapes without the limit of the actual Geoboard. The Geoboard gives the user a virtual rubber band which can then be stretched over the pegs in the board. Use the rubber band to construct shapes and study the relationship between the the shape of the rubber band and the area inside the rubber band.


Drag any of the vertices of the polygon to change it's shape. Click the mouse near the border of the polygon and drag to create another vertex at that point. Double-click on a vertex to delete that vertex.


  • Add: Click to insert a new rubber band of the current color.
  • Remove: Click to remove the selected rubber band.
  • Show/Hide Area: Click to show/hide the area and perimeter information.
  • Show/Hide Sides: Click to show/hide the side lengths.
  • Click the buttons along the bottom to change the current color. If a rubber band is selected, its color will change.

The Purpose:

  • Constructing shapes is much easier than on a real Geoboard and without the limit of the length of the rubber bands.
  • Learn the relationship between the shape of the object and its area.
  • Advanced: Determine how the area inside the rubber band can be easily calculated without having to measure anything.

The Simulation:


If you are having trouble loading the Applet, a possible solution is to update your Java Runtime Environment. To update your JRE, go to SUN's Java Webpage and follow the links to download the Java software.

If you are having problems using the applet, please notify Pavel Safronov. Please specify the applet you are using, your web browser, operating system and the particular problem experienced. Please be as detailed as possible.

The Credits:

Applet designed and coded by Pavel Safronov.

Geoboard animation created by Linda Stojanovska.

Download the sample HTML and CLASS files as a RAR archive: Geoboard

Please e-mail us with comments, error reports or complaints you have about the applet.


Social Media Links:

Connect with us

Additional navigation options:

© 1994-2023 MSTE | 505 East Green St., Suite 202, Champaign, IL 61820 | (217) 244-7486