Circle Maker | Instructions: | Suggested Lessons or Activities: | Special Features: | Other Related Modules and Useful Links:

Circle Maker

© R. Mirshahi


  • Click the circle maker button with the arrow pointing to it to make a new circle at random. You will see the circle's measurements (radius, diameter, area, and perimeter). The radius (r) is close to its line segment on the circle and the other measurements are at the top right of the page. You can hide the diameter, Area, and Perimeter by clicking the "eye" and calculate the diameter, area and perimeter. Click the "eye" again to reveal the measurements and check your answers (test yourself). You can also estimate and use the ruler to measure the radius yourself. When you click the ruler button on the tool bar, the ruler will appear properly position with the zero point on the centre of the circle. You can move and turn the ruler as desired. Clicking the ruler button again will hide the ruler (toggle switch). You can annotate using the pen tool (e.g., to show your calculations). Click eraser to remove your writing. The measurements are rounded to the nearest mm. The area is in squared mm.

Suggested Lessons or Activities:

  • This is a good resource for estimating and measuring area and perimeter of a circle.
  • Explore how you can calculate
the area of a circle (Area = r x r x Л) Pi is rounded to 3.14 for our calculations
and the perimeter: (Perimeter= 2 x r x Л) Pi is rounded to 3.14 for our calculations

As you click the reset button, the Main Activities Resource is loaded here. If you are looking for details and specific instructions and lesson ideas about the other activities, you need to go to the pages where these resources are housed.
  1. Angle Maker
  2. Line Maker
  3. Rectangle Maker
  4. Draw and Measure Lines and Angles
  5. Linear Measurement Test 20 Questions
  6. Triangle Maker

Special Features:

  • random circle maker
  • automatic measurements of radius, diameters, areas and perimeters
  • ability to hide measurements
  • ability to annotate
  • interactive ruler (click the ruler button on the tool bar to show or hide ruler)
  • works really well with interactive whiteboards and Flash enabled tablets
  • full screen (minimize distractions as well as maximize the use of screen space)

Other Related Modules and Useful Links:

geometry resource (identify 2D shapes and 3D solids - also includes animated shapes and 3D animations of solids)