The Fujita-Pearson Scale

Fujita - Pearson Tornado Scale 
Category: F0         
Wind  Speed:  40-72mph 
Damage: Chimney damage, tree branches broken
Category: F1
Wind  Speed: 73-112mph
Damage: Mobile homes pushed off foundation or overturned
Category: F2
Wind  Speed: 113-157mph
Damage: Considerable damage, mobile homes demolished, trees uprooted
Category: F3
Wind  Speed: 158-205mph
Damage: Roofs and walls torn down, trains overturned, cars thrown
Category: F4
Wind  Speed: 207-260mph
Damage: Well-constructed walls leveled
Category: F5
Wind  Speed: 261-318mph
Damage: Homes lifted off foundation and carried considerable distances, autos thrown as far as 100 meters