Because the distance between the Earth and the Sun varies, this should (strictly speaking) be qualified by the word 'mean'. An astronomical unit is the mean distance between the centre of the Earth and the centre of the Sun. It's now defined as 1.4959787 x 1011 metres, or 9.2955807 x 107 miles. As every schoolboy should know, this is just under 150 million kilometres, or just under 93 million miles.
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