Lake Michigan is about 118 miles wide at its widest point.

Quick Scoop

  • Maximum width: 118 miles.
  • Length: about 307 to 321 miles, depending on the source and measurement used.
  • Average width: smaller than the maximum; some references describe it as averaging around 75 miles across.

For a simple answer, 118 miles wide is the number most people use when asking how wide Lake Michigan is.