A map of the Mid-Atlantic Ridge. The Mid-Atlantic Ridge (MAR) is a mid-ocean ridge, a divergent tectonic plate or constructive plate boundary located along the floor of the Atlantic Ocean, and part of the longest mountain range in the world.
Since the distances are so large, we usually express them in Astronomical Units (AU). (An AU is the average distance from Earth to the Sun, about 150 million kilometers or 93 million miles.) The table below lists the distance of each planet from the Sun in AU. (Numbers were taken from this page.)
First the short answer. Mars has an average distance from the Sun that is about 1.5 times that of the Earth's average distance from the Sun. This means that when Earth and Mars are closest to each other, the distance would be about 1.5 - 1.0 =0.5 times the average distance of Earth from the Sun. When Earth and Mars are on opposite sides of the Sun, the distance between would be about 1.5 + 1.0 = 2.5 times the average distance of the Earth from the Sun.