Tornadoes are classified by the Wind Speed, Path Width and Path Length. Although the the path width and path length are not widely used today, you may find them in some articles and literature on tornadoes. The National Weather Service scales tornadoes by intensity on a scale of - to 5 on the Fujita-Pearson scale which include:
F- 0. Light damage. Wind up to 72 mph. Some damage to chimneys; breaks branches off trees; pushes over shallow-rooted trees; damages sign boards.
F- 1. Moderate damage. Wind 73 to 112 mph. 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. Considerable damage. Wind 113 to 157 mph. 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 damage. Wind 158 to 206 mph. Roof and some walls torn off well-constructed houses; trains overturned; most trees in forest uprooted.
F- 4. Devastating damage. Wind 207 to 260 mph. Well-constructed houses leveled; structures with weak foundations blown off some distance; cars thrown and large missiles generated.
F- 5. Incredible damage. Wind above 261 mph. 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.