quality:correction
Frequency

The diameter of the largest impactor to hit Earth on any given day is likely to be about 40 centimeters (16 inches), in a given year about four metres (13 ft), and in a given century about 20 m (66 ft). These statistics are obtained by the following:

Over at least the range from five centimeters (2.0 inches) to roughly 300 meters (980 feet), the rate at which Earth receives meteors obeys a power-law distribution as follows:

where N (> D) is the expected number of objects larger than a diameter of D meters to hit Earth in a year. This is based on observations of bright meteors seen from the ground and space, combined with surveys of near-Earth asteroids. Above 300 m (980 ft) in diameter, the predicted rate is somewhat higher, with a 2 km (1.2 mi) asteroid (one teraton TNT equivalent) every couple of million years – about 10 times as often as the power-law extrapolation would predict.