According to some estimates, an asteroid the size of Apophis can be expected to strike Earth about every 80,000 years. The best estimate puts it at 270 meters (885 feet across), and it has a mass of 2.1 x 10 10 kg. after a series of studies, astronomers no longer predict an asteroid impact in 2029. For comparison, the object … Courtesy of NASA.gov Asteroid Apophis is 370 meters in width. (The Eiffel Tower is 324 meters in height.) As well as these figures (all sourced from … Apophis is about 0.3 kilometers in diameter, making it small in absolute terms, but larger than 90% of asteroids, comparable in size to the U.S. Capitol building. But, they note that Apophis could hit Earth sometime in 2036 or 2068. If calculations made by NASA is correct, … So back to the original question, how big is Apophis? Apophis is considered one of the dangerous space bodies that will skim past the earth in the next ten years. The rotation of Apophis has been observed. It completes a rotation on its axis every 30.40 days. A very simple comparison gives Apophis at about 380 metres in diameter and Tunguska about 50 to 190 metres diameter.