Intervals of time are average timespans, which means that the NEOs considered may hit at that interval, or at a earlier, or later date

Diameter	Hit Frequency	Damages
large (6 miles, about 10 km)	1 every 26-30 million years (some sources say 100 million years); as of early 2019 NASA deemed the likelihood of a 3-6 miles (5-10km) in diameter hitting the Earth is only 0.000001 percent	mass extinction class. It's such objects which triggered the end of the dinosaurs 70 million years ago (with a size 2.5-12.4 miles -4-20 km) or some other mass extinction during geologic times Impactors of a size 62 miles (100 km) would destroy entirely the Earth's crust and eject the atmosphere into space. Few such impactors likely hit early at Earth, when life hadn't started yet and no any are likely to occur until the death of the Sun. Objects 6.2-62 miles (10-100 km), hitting every 20 million years would have hindered the development of life, leaving not enough time between blows to recover and reducing the life's diversity. The asteroid which caused dinosaurs' demise is supposed to have had a diamter of 5.6 miles and gouged a crater 930-mile wide in a shallow sea off the coast of Yucatan, current Mexico. He also caused a 300-foot high tsunami which was moving by more than 60 mph! The asteroid likely stroke with a speed of 43,500 mph as some ejectas reached up to 24,800 mph with some the size of a small town or others reaching the liberation speed, a speed beyond which a object cut loose from the Earth gravity. Most ejectas eventually fell back to the surface and triggered a global wildfire, night conditions for 6 months, a nuclear winter for 6 years and then a global warming. A 1.7 miles long asteroid passed Earth by 3.6 million miles late May 2013, the sole expected passage of that object for at least the next 200 years
0.6 miles (1 km)	1 every 500,000-800,000 years (100,000 years?)	civilization or regional-sized damages. Billions of people die, the Earth's surface is transformed into an oven. Sun rays blocked for at least a growing season, maybe more. Threshold for a NEO winter in the 1,300 ft (400 m) range
1,000-1,300 ft (2,000 ft?) (300-400 m (600 m?)	?	would flatten everything in an area the size of the state of New Jersey in the U.S.A. and kill everybody; debris in the atmosphere affecting agriculture for months; tsunamis hundred of feet high would destroy coastal cities. Such asteroids fly by the Earth every 25 years at the distance of the Moon
660ft (200 m)	1 every 100,000-160,000 years	threshold of country (European-style) killers"; 15 ft (5 m)-high tsunamis
150-300ft (50-140 m)	1 every 1,000-3,000 years	Tunguska object class; city flatteners (the Tunguska object might have been of a size of 120 ft and such objects might hit every 300 years or even 100 years). Even such 100-meter wide objects are damageable as they explode in the Earth's atmosphere, yielding a massive shock wave below. Such Tunguska NEOs have flattening effects regionwide
200 ft (60 m)	1 every 30-100 years	may destroy a city. The object which created the 0.6-mile wide Meteor Crater, in the USA, had a size of 150 ft as some estimates bring to that such objects may hit every 50,000 years
100ft (30 m)	1 every 100 years	may trigger regional damages; such objects have a power of 1 megaton, 7 times the Hiroshima bomb that is. The current state of observational science doesn't allow to spot such objects more than 3 days ahead that they strike Earth! Some sources are stating that 70-ft (21-meter) wide objects and likely the ones of this category are grazing Earth every few months by a distance of 40,000 miles (64,000 km). Some studies are stating that the Tunguska object might have been of a diameter of 65 ft (20 m) only as the damage might have been due mostly to a wave effect and the explosion at 3 to 5 megatons. Such objects thus might trigger Tunguska-like devastation every couple of centuries only. The February 15th, 2013 Chelyabinsk meteor hit that region of Russia shortly after dawn as it was measuring 59 feet (18m) across and weighing 11,000 metric tons. Its speed reached 41,600 mph (66900 km/h) and it exploded in altitude, with a peak at 19 miles (30 kilometers) above the city of Chelyabinsk, generating a bright, hot explosion with a gas cloud, as well as a large shock wave that broke windows and knocked down parts of buildings and structures, injuring some 1500 people by flying glass and other debris. It released more than 30 times the power of the Hiroshima atom bomb! The Chelyabinsk meteor was of the Apollo class of Earth-crossing asteroids. The explosion also deposited hundred of tons of cohesive and persistent dust into the stratosphere. Larger, heavier particles lost altitude and speed, while their smaller, lighter counterparts stayed aloft and retained speed inside the jet stream current, eventually forming a ring above the northern hemisphere. It persisted during three months. The Chelyabinsk meteor constituted the first NEA impact disaster in modern history
33 ft (10 m)	1 every 10 years	1 such NEO, which number total by 50 million, is passing almost daily within a lunar distance, as one is striking the Earth's atmosphere about every 10 years on average. They may be discovered with a 3-day notice. Damage potentiality is unknown. Stony asteroids less than 84 ft (25 meters) wide break up in Earth's atmosphere and not cause ground damage
10-15 ft (3-5 m)	1 every 200-400 years	300 ft-wide (100 m) craters; objects of the sort, of the iron-made type break apart under 50 meters wide
- (objects of 25 kilotons of TNT)	1 every 4 years	it might that 23-ft wide objects pass about 8,700-mile (14,000 km) close to Earth about twice a year and are impacting down to the surface about every 5 years. Flybys of such small NEOs within the Moon's orbit occur every few week
several feet (about 1 meter) (objects of 5 kilotons of TNT)	1 each year	break apart in the atmosphere under the form of a fireball, through a single shot or a sequence of explosions. Five-meter-sized NEOs from a undiscovered population of about 30 million would be expected to pass daily within a lunar distance, and one might strike Earth's atmosphere about every 2 years on average. If one is to enter Earth’s atmosphere, it it would be expected to burn up high in the atmosphere and cause no damage to Earth’s surface

note: some discrepancies are due to comprehensive studies not available yet as our site proceded from various sources

The dangerousness of the impacts depends on the level to which the asteroids explode: from the upper atmosphere (all objects under 160 ft -or 50 meters; two or three dozen objects every year) to relatively near the surface (the Tunguska-class objects explode at a relatively low altitude and trigger a shock wave -and this wave is what causes damages (in Siberia, the wave had flattened 1200 square miles forest)). A 2003 joint English-Russian study showed that asteroids twice the one of the Tunguska hit less often (but have a greater chance to hit the ground and to yield local havoc and tsunamis), that 200 metres objects -yielding 5 m high tsunamis- hit only once every 160,000 years and that many more asteroids blow up in the atmosphere than previous estimates yielding so less tidal waves (of them stony ones which are blown up even when of size up to several hundred meters in diameter; moreover these sizeable stony asteroids, generally speaking, endure the "fragmentation model", being torn apart at high altitudes)

Object which triggered dinosaurs disparition 65 million years ago was a 10 km wide object and a recently discovered crater thought to be the mark of an asteroid having another major mass exitinction 250 million years ago -the Great Dying (end of Permian)- is thought to have been in this order of magnitude too

To know too: since 3 billion years, asteroids which disappeared by hitting planets or whichever other way are replaced by others, this leading to a balance of their number