Question

How deep would you have to drill to reach the center of earth?

Answer 1

The radius of the Earth is about  3,960  miles.

That's how far the center of the Earth is straight down under your feet. 
It's farther than the distance all the way across the USA, from New York
to Los Angeles.  It's like the distance from London (England) to Chicago.

If you drill absolutely straight and aim straight down, that's how far
you need to drill to reach the center.  Unfortunately, your drill will melt
long before you get there.

The longest hole ever drilled into the Earth (so far) is the Sakhalin-I Oduptu Well,
drilled by Russia into the sea-bottom in 2011. 

That hole is 40,502 feet ... roughly 7.67 miles, or about  0.0019 of the distance
to the center of the Earth.  You can see that we still have quite a long way to go !