| F0 | 40-72 mph | Gale Tornado--light damage. Some damage to chimneys; break branches off trees; push over shallow-rooted trees; damage sign boards. |
| F1 | 73-112 mph | Moderate Tornado--moderate damage. The lower limit is the beginning of hurricane wind speed; peel surface off roofs; mobile homes pushed off foundations or overturned; moving autos pushed off the roads. |
| F2 | 113-157 mph | Significant Tornado--considerable damage. Roofs torn off frame houses; mobile homes demolished; boxcars pushed over; large trees snapped or uprooted; light-object missiles generated. |
| F3 | 158-206 mph | Severe Tornado--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 mph | Devastating Tornado--devastating damage. Well-constructed houses leveled; structures with weak foundations blown off some distance; cars thrown and large missiles generated. |
| F5 | 261-318 mph | Incredible Tornado--Incredible damage. Strong frame houses lifted off foundations and carried considerable distance to disintegrate; automobile-sized missiles fly through the air in excess of 100 meters (109 yds.); trees debarked; incredible phenomena will occur. |
| F6 - F12 | 319 mph - MACH 1 (speed of sound) | The maximum wind speeds of tornadoes are not expected to reach the F6 wind speeds. |