The most widely used method to calculate tornado damage is the Fujita scale, known by its shorter name, the F-scale, which was developed by Dr. T. Theodore Fujita. Wind speeds are based on calculations of the Beaufort wind scale and have never been scientifically verified in real tornadoes. In the Fujita scale, wind speed is not measured directly but rather estimated from the amount of damage. Tornado width is estimated by the path of destruction -- which can be up to one mile wide.

The interactive tornado below will help you understand how scientists and meteorologists determine the F-scale of a tornado. Select the width of the tornado. Next, select the core pressure difference. This is the difference between the pressure inside the tornado and the pressure outside of the tornado. The greater the difference, the greater the wind speeds.

When you have set the width and pressure, click on "GO". After the tornado has passed by, examine the amount of damage. Refer to the F-scale table below the activity, and choose which F-scale you would assign to the tornado, based on the damage you see.