Question

How much miles is a light year

Answer 1

1 light-year = roughly  5,874,601,700,000 miles.  (rounded)

To work it out, take the speed of light, and change units a few times:

          (186,282.397 miles/second)
times
          (86,400 second/day)
times
          (365 day/year)

    =   (186,282.397 x 86,400 x 365)  mile/year .

You can whip that out on your calculator in no time.