Yesterday, a 60-foot asteroid flew by Earth and missed us, but there's always a risk that one will eventually hit.
So how bad would it be? There are several fun (and scary) calculators that let you figure out just what damage a certain size asteroid might do to a certain location. Each is a little different, but they certainly give you a sense of how disastrous a big asteroid can be.
1) See how an asteroid could destroy your hometown
To send an object down on any location of your choosing, head to the interactive at the Killer Asteroids project, run by The Space Science Institute.
This calculator has a simple interface that lets you pick a small, medium, or large asteroid or comet and input any address for a target. For example, this is what happens when a medium asteroid strikes Vox.com HQ. The resulting map shows rings of damage, from the crater itself to "clothing ignites" to first-degree burns.
2) Customize your Earth-destroying asteroid
If you'd prefer to finely tune your asteroid's size, speed, and other characteristics and get very thorough results, try the Impact: Earth! calculator at Purdue.
This calculator doesn't let you send the asteroid to a specific geographical spot and doesn't provide an image of what would happen.
However, it does spit back just about every possible known variable that can be calculated about an impact. That includes the energy equivalent in megatons of TNT, earthquakes, what kind of meteoroid-resulting junk ("ejecta") is going to fly how far, any changes in Earth's tilt, and even when a resulting tsunami would arrive and how high its waves will be. And you can drill down into all of them for a more thorough explanation.
This calculator also allows you to recreate famous events, like the Tunguska fireball of 1908, and adjust them however you want. For example, this is what happened when I imagined standing 50 miles away from the giant projectile that fell on Chesapeake Bay some 35 million years ago:
3) See how big a crater the asteroid would leave
You can also try the Down 2 Earth simulator. It's available in five languages and has a thorough selection of projectiles of varied sizes, densities, strike angles and speeds. However, its visual output is limited to only the crater footprint. (It does spit out some other values such as the Richter magnitude and fireball radius, but doesn't visualize them.) This interactive was created by Andrew Scott of the University of South Wales and Western Carolina University.
Here's the crater from a hunk of dense rock 6 miles across hitting Central Park head-on at 100,000 mph:
And here's the depth of the crater, compared to the Eiffel Tower:
Further reading: An asteroid will just miss Earth today. We won't always be so lucky.