from the BBC BBC
Pulled from text above: impact effects calculator .Want to know what would happen if a 10km-wide asteroid came out of the sky and slammed down on your city?Scientists at Purdue University and Imperial College London have updated their popular impact effects calculator first produced in 2004.
Users dial in details about the hypothetical impactor, like its diameter and density.
The web program then estimates the scale of the ensuing disaster, such as the size of the crater left behind.
It will also tell you how far away you need to be to avoid being buried by all the material thrown out by the blast, or set on fire.
Note that for those in the United States, the distance from Los Angelos to New York City is about 3000 miles or 5000km. I also found it interesting that the distance across the United States is very slightly larger than the diameter of the moon.