Parameters
The five categories are listed here, in order of increasing intensity.
- Where the relative frequency of tornadoes is mentioned, it is the relative frequency in the United States, for which the best data exists. Strong tornadoes (F2 or greater) occur less often elsewhere in the world. The ratio seems to be similar except for some areas where it's less such as the United Kingdom, but because of few overall number of tornadoes there are few strong tornadoes. Areas of eastern India, and possibly a few other areas do have frequent severe tornadoes; however, data are scarce and statistics in these countries have not been studied thoroughly.
- The rating of any given tornado is of the most severe damage to any well-built frame home or comparable level of damage from engineering analysis of other damage.
| Scale | Estimated wind speed* | Relative frequency | Average Damage Path Width (meters) | Potential damage | ||
| mph | km/h | |||||
| F0 | 40–72 | 64–116 | 38.9% | 10–50 | Light damage.
Some damage to chimneys; branches broken off trees; shallow-rooted trees pushed over; sign boards damaged. |
|
| F1 | 73–112 | 117–180 | 35.6% | 30–150 | Moderate 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. |
|
| F2 | 113–157 | 181–253 | 19.4% | 110–250 | Significant damage.
Roofs torn off frame houses; mobile homes demolished; boxcars overturned; large trees snapped or uprooted; highrise windows broken and blown in; light-object missiles generated. |
|
| F3 | 158–206 | 254–332 | 4.9% | 200–500 | 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. |
|
| F4 | 207–260 | 333–418 | 1.1% | 400–900 | Devastating damage.
Well-constructed houses leveled; structures with weak foundations blown away some distance; cars thrown and large missiles generated. |
|
| F5 | 261–318 | 419–512 | <0.1% | 1100 ~ | Incredible damage.
Strong frame houses lifted off foundations and carried considerable distances to disintegrate; automobile sized missiles fly through the air in excess of 100 m (109 yd); trees debarked; steel reinforced concrete structures badly damaged. |
|
Since the Fujita scale is based on the severity of damage resulting from high winds, an F6 tornado is a purely theoretical construct. Property damage cannot exceed total destruction, which constitutes an F5. (A tornado with windspeeds greater than 319 miles per hour is theoretically possible, and the 1999 Oklahoma City tornado may have been such an event. However, no such wind speed has ever been recorded and that measurement was not near ground level.)
Read more about this topic: Fujita Scale
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