The relative distance of Mercury to the Sun depends on what you're looking for:

* Average distance: Mercury is about 0.39 AU (Astronomical Units) from the Sun.

* Orbital distance: Mercury's orbit is highly elliptical. It ranges from 0.31 AU at perihelion (closest to the Sun) to 0.47 AU at aphelion (farthest from the Sun).

So, the relative distance of Mercury to the Sun can be expressed as:

* Average: 0.39 times the distance between the Earth and the Sun.

* Perihelion: 0.31 times the distance between the Earth and the Sun.

* Aphelion: 0.47 times the distance between the Earth and the Sun.