Finding π Experimentally

In this activity you will find a good estimate for $\large~\pi$ using the same technique mathematcicians used thousands of years go.


  1. Collect measurements from at least four different circles and record the data in this table.
  2. Use the metric system for your measurements.
  3. Use a calculator to find the ratio $\frac{C}{d}$.
  4. Round your answers to the nearest 100th place.
  5. Calculate the mean average and the median average of your $\frac{C}{d}$ ratio. 




































  1. Use the green dot to change the size of the circle.
  2. Notice the diameter and circumference change as the circle changes.
  3. How is the length of the circumference related to the length of the diameter? How many diameters can fit onto the circumference?
  4. Where in this applet can you find $\large~\pi$?



  1. Use the BLUE dot to change the diameter of the circle.
  2. Pull the "RollTheCircle" slider to roll the circle and "unwrap" the circumference.
  3. Notice how many diameters it takes to equal the circumference.
  4. Where in this applet can you find $\large~\pi$?