Eight Patch quilt blocks are designed on a 8 x 8 grid, hence the name. Although this grid is the basis of the designs, often larger pieces are used. The math in an eight patch is usually quite easy, as often quilt blocks are made in sizes 8", 12" or 16" measurements.
Eight patch blocks are usually chosen by experienced quilters due to the number of pieces in the block (but don't let that deter you). Sewing a precise quarter inch seam allowance is necessary in order to match one patch to the next patch. More seams means more chance of error, and these small errors add up. But ... I hope this last note does not deter you from trying out some of these amazing quilt blocks.