Various sources state the first Death Star has a diameter of between 140 and 160 kilometers. There is a broader range of figures for the second Death Star’s diameter, ranging from 160 to 900 kilometers.
Why does the Death Star have a hole?
The Death Star’s thermal exhaust port was a significant flaw in the design that the Rebels were able to exploit during the Battle of Yavin. This led to the thermal exhaust ports to be removed for the Death Star II, although the Death Star III retained this weakness.
Can the Death Star move?
The Death Star’s hyperspace motivator units were comprised of linked banks of field generators such as those found aboard Imperial Star Destroyers. One hundred twenty-three individual hyperspace generators, tied into a single navigational matrix, were necessary to carry the Death Star beyond the speed of light.