Equation to determine Crater Size:

D=0.07Cf(ge/g)1/6(W pa/pt)1/3.4

Where:

D = Crater Diameter

Cf = Crater Collapse Factor ( this is equal to 1.3 for craters >4km on Earth)

ge = Gravitational Acceleration at the surface of Earth

g = Acceleration at the surface of the body on which the crater is formed

W = Kinetic Energy of the impacting body (in kilotons TNT equivalent)

pa = Density of the impactor (ranging from 1.8g/cm3 for a comet to 7.3g/cm3 for an iron meteorite).

pt = Density of the target rock

Note: Typical impact velocities for asteroids are around 20km/s and approximately 60km/s for comets.