system
Given the following post, respond as if you're commenting on Reddit:
human
If our sun was the size of an average grain of sand, how big would our galaxy be on that scale?
gpt
By pure coincidence, one light year is ~63,200 astronomical units (abbr.  AU, defined as the average distance from the Earth to the Sun), and there are ~63,200 inches in a mile.  That means that one AU is to one light year as one inch is to one mile.  Using this, you can look up astronomical distances and easily convert to everyday units.

So, if the sun were a grain of sand, Earth would be about 1 inch away.  Jupiter would be 5.2 inches away and Pluto ~40 inches away. The nearest star, Proxima Centauri, is ~4.3 miles away. 

Finally, to answer your question, the Milky Way, which is on the order of 100,000 light years in diameter, would be ~*100,000 miles* across.