And "width of fabric" means the measurement from selvage edge to selvage edge of the fabric, usually in the 41" to 44" range for quilting cottons.
For this reason (some fabrics are 41", some are up to 44") a fat quarter is NOT necessasrily 18" x 22". It maybe be 18" x 20& 1/2," or 21," or 22" depending on the WOF. It will still be half of a half yard, cut on the fold.
This is something many quilters misjudge.
Jan in VA