Earth's orbit is not perfectly circular. It has an eccentricity of 0.0167 (where zero is perfectly circular and 1 is a straight line).
Aphelion (the farthest distance from Helios/Sol/Ra/Sun) = 152.1 million kilometers (94.53 million miles)
Perihelion (the closest distance to the sun) = 147.1 million kilometers (91.42 million miles)
The average is 149.6 million kilometers (92.977 million miles), and this is the basis for the Astronomical Unit (A.U.)
The distance to the sun can also be measured by light speed -- roughly 8.31 light minutes.