The answer to your question, that how many miles is it from earth to mars, is very easy to know. Because of huge satellites which are being sent to mars in search of life from many countries, we have discovered a lot about mars. According to experts, earth and mars reaches to their closest points in every 26 months.
This situation is considered as opposition of mars as the location of sun and mars in totally opposite to each other in relation to earth. When this opposition takes place, the planet is visible with a red tint in the sky from earth. And this also gives mars a name, i.e. the red planet.
Mars is also the fourth planet from sun, which is located between Jupiter and earth. Its distance from sun is not only opposite but is also much further away, than that of the earth and sun. The distance between the sun and mars is said to be 140 million miles.
Mars can reach about 128 million miles closer to the sun whereas it can even travel around 154 million miles away from it. The assumed distance between mars and earth is said to be between 40 to 225 million miles. The distance between these two planets keeps on changing throughout the year because of the elliptical path in which all the planets rotate.
As the distance between mars, sun and earth is so much high, it takes a Martian year, for mars to go around the sun. The Martian period includes a time of around 687 earth days. This means that, it takes more than 2 years for the mars to reach its initial rotation point.
If we talk about one Martian day, it is the total time which is taken by a planet to spin around once. This day usually lasts longer than our regular earth days. So this was the actual reason which states the distance between earth and mars.