GPA really different

<p>According to my school, my unweighted GPA is about 3.6. I was on a college website though, and noticed that according to their calculations, my GPA is 3.9. I'm really confused about this. Could somebody explain the "standard scale" for GPA at colleges?</p>

<p>Unweighted is as follows - A=4, B=3, C=2, D=1.</p>

<p>Take the average</p>