Wind speed and Related property damages are the basis of the 'Fujita Scale' for classifying tornadoes. 'Fujita Scale' for classifying tornadoes: In 1971, Dr. Theodore Fujita developed a method for categorizing tornadoes by looking at how much damage they cause and using this to estimate the wind speed. This system is called the F-Scale or Fujita Scale; it classifies tornadoes by their estimated wind speed, which is determined by looking at how strong the wind must have been to cause the resulting damage. Tornadoes are classified into five categories, F-0 through F-5. F-0 tornadoes are the mildest. F-5 tornadoes are the most dangerous (and the rarest). ​F-0 40-72 mph, Light damage, chimney damage, tree branches broken F-1 73-112 mph, Moderate damage, mobile homes pushed off foundation or flipped over F-2 113-157 mph, Considerable damage, mobile homes demolished, trees uprooted F-3 158-205 mph, Severe damage, roofs, and walls were torn down, trains overturned, cars thrown around F-4 207-260 mph, Devastating damage, well-constructed walls leveled F-5 261-318 mph, Violent damage, homes lifted off the foundation and carried considerable distances, autos thrown as far as 100 meters. It is not easy to measure wind speed in a tornado because a tornado usually destroys local measuring equipment, and tornadoes exist for a short time at random places and they are gone before meteorologists can study them.