How to calculate polygon areas in acres or square miles instead of feet?

Question

I have a layer in State Plane NAD83. When I use "Vector|Geometry Tools|Add/export geometry columns" or Field Calculator they both create the area in feet.

What if I want acres or square miles?

Calculating polygon areas in shapefile using QGIS

Answer 1

If you want to calculate acres in QGIS, open the field calculator and and use the following code:

$area / 43560