how big was the asteroid that killed the dinosa... =~

The asteroid that wiped out (most) of the dinosaurs is estimated to have been roughly 10–15 kilometers (about 6–9 miles) across, similar in width to a large city like New York’s Manhattan stretched out and scaled up.

Quick Scoop: How Big Was It?

• Diameter: About 10–15 km (6–9 miles).

• Crater size: It blasted out the Chicxulub crater in today’s Yucatán, which is about 180 km (110 miles) wide and around 20 km deep.

• Speed: It was likely moving at around 20 km per second (tens of thousands of km/h) when it hit, which made its energy absolutely massive.

In other words, the rock itself was “only” the size of a small region, but the explosion was equivalent to tens of millions of megatons of TNT, enough to reshape the planet’s climate.

What That Size Actually Means

Scientists compare its destructive power to:

• Global firestorms triggered by superheated ejecta falling back through the atmosphere.

• Mega-tsunamis racing across ancient oceans.

• A “nuclear winter” style impact winter as dust and aerosols blocked sunlight, collapsing food chains on land and in the sea.

A useful mental picture: a rock only a few times bigger than Mount Everest, hitting so fast that it briefly outshone the sun in its region and turned an entire day into the beginning of a mass extinction.

Forum / Trending Angle

This question pops up a lot on science YouTube and forums, where people are often surprised the asteroid wasn’t “planet-sized” at all—just a few dozen kilometers wide.

Discussions usually focus on how it’s the speed and energy release, plus where it hit (a shallow sea loaded with sulfur- and carbon-rich rocks), that made such a “small” object so globally deadly.

“It was only about 10 km wide, but it hit with the force to end an era.”

Mini FAQ

1. Was it the biggest impact ever?
   No. Earth has older, even larger impact structures, but this one is the largest in the last billion years and the one tied directly to a mass extinction.

2. Is the asteroid still around?
   No. It vaporized and melted on impact; what remains is the buried Chicxulub crater and global layers of debris and iridium-rich dust.

3. Could something that size hit again?
   Objects of that scale exist, but modern surveys track many of the biggest near‑Earth asteroids, and international efforts focus on deflection long before they become a threat.

Information gathered from public forums or data available on the internet and portrayed here.