Depending on when you measure the distance from Mars to Earth it can be as little as 34 million miles or as much as 249 million miles. Since both planets orbit the sun independently it is always changing. You can find more information here: http://www.universetoday.com/guide-to-sp...

The distance between Mars and Earth depends on where each planet is in it's orbit. Mars came closer to Earth on August 27, 2003, than it has been in 60, 000. On that day it was 55, 758, 006 kilometers away. On average, Mars is about 78, 000, 000 kilometers away.