Asteroids headed for Earth are scary. So get to know them a little! You can use the Impact: Earth! calculator to see what kind of damage an asteroid will cause. It's totally not as scary when you crunch the numbers.
The Impact: Earth! calculator was developed by a Purdue University research team and it basically lets anyone calculate the damage an Earth-bound asteroid will cause. You'll have to fill in the basic info of your presumed asteroid like how big it is, how dense it is, the angle of entry and the location of its hit. But after those numbers are thrown in, the calculator will spit back the scientific consequences: like the size of the crater, the seismic effects, the energy of the impact, the ejecta, and other scary results of an asteroid.
Things get a little hairy if an Empire State Building-sized asteroid landed here—gnarly fireballs are created, a magnitude-7.7 earthquake would hit and some huge ass crater will form—but I'm totally cool with a humpback whale sized asteroid. [Impact: Earth! via Pop Sci]