F-1: Moderate tornado
Wind Speed: 73-112 mph
Damage: The lower limit is the beginning of hurricane wind speed; peels surface off roofs; mobile homes
pushed off foundations or overturned; moving autos pushed off the roads; attached garages may be
destroyed.
F-2: Significant tornado
Wind Speed: 113-157 mph
Damage: Considerable damage. Roofs torn off frame houses; mobile homes demolished; boxcars
pushed over; large trees snapped or uprooted; light object missiles generated.
F-3: Severe tornado
Wind Speed: 158-206 mph
Damage: Roof and some walls torn off well-constructed houses; trains overturned; most trees in forests
uprooted.
F-4: Devastating tornado
Wind Speed: 207-260 mph
Damage: Well-constructed houses leveled; structures with weak foundations blown off some distance;
cars thrown; large missiles generated.
F-5: Incredible tornado
Wind Speed: 261-318 mph
Damage: Strong frame houses lifted off foundations and carried considerable distances to disintegrate;
automobile-sized missiles fly through the air in excess of 100 meters; trees debarked; steel-reinforced
concrete structures badly damaged.
F-6: Inconceivable tornado
Wind Speed: 319-379 mph
Damage: These winds are very unlikely. The small area of damage they might produce would probably not be recognizable along with the mess produced by F4 and F5 wind that would surround the F6 winds. Missiles, such as cars and refrigerators would do serious secondary damage that could not be directly identified as F6 damage. If this level is ever achieved, evidence for it might only be found in some manner of ground swirl pattern, for it may never be identifiable through engineering studies
National Severe Weather Laboratory