The Fujita Tornado Scale

The Fujita scale or F-scale was developed by Dr. T. Theodore Fujita of the University of Chicago in 1971.  Using the damage inflicted on man-made structures, Dr. Fujita defined six categories of tornado intensity ranging from weak F0 to violent F5.  National Weather Service personnel continue to use the F-scale today, making surveys of damage caused by tornadoes and assigning a rating.

Fujita Rating

Estimated Wind Speed

Typical Damage




Less than 73 mph

Light Damage - Some damage to chimneys; branches broken off trees; shallow-rooted trees pushed over; sign boards damaged.



73-112 mph

Moderate Damage - Peels surface off roofs; mobile homes pushed off foundations or overturned; moving autos blown off roads.



113-157 mph

Considerable Damage - Roofs torn off frame houses; mobile homes demolished; boxcars overturned; large trees snapped or uprooted; light-object missiles generated; cars lifted off ground.



158-206 mph

Severe Damage - Roofs and some walls torn off well-constructed houses; trains overturned; most trees in forest uprooted; heavy cars lifted off the ground and thrown.



207-260 mph

Devastating Damage - Well-constructed houses leveled; structures with weak foundations blown away some distance; cars thrown and large missiles generated.



261-318 mph

Incredible Damage - Strong frame houses leveled off foundations and swept away; automobile-sized missiles fly through the air in excess of 100 meters (109 yds); trees debarked; incredible phenomena will occur.

Less than 1%


tornado imageIt is important to remember that the wind speeds listed are only very rough estimates and have not been scientifically analyzed.  The Fujita scale ratings are assigned subjectively and there is a lot of variation in damage depending on how well structures are built.  In addition, the tornado rating is not based on the size of the funnel or strength of the wind, but the damage inflicted.   Thus, if a tornado occurs in an open area where no buildings are present, it could be assigned a weaker F-rating than if it hit a man-made structure.



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