The distance between Earth and Mars varies depending on their positions in their respective orbits around the Sun. On average, the distance between the two planets is about 225 million kilometers (140 million miles). However, this value can range from about 55 million kilometers (34 million miles) at their closest approach (known as opposition) to around 401 million kilometers (249 million miles) at their farthest distance (known as conjunction). The average distance of 225 million kilometers is often used as a reference point for interplanetary missions and calculations involving travel between Earth and Mars.