Lay the acrylic ceiling panel on a flat, sturdy table. If the panel has a decorative side, make sure it is facing downward.
Place a tape measure onto the panel to determine where you need to cut it at.
Place a straight edge at the desired cutting location and use a dry erase marker to draw a cut line on the panel.
Keep the straight edge in place and hold it down firmly with your hand. Place the blade of a utility knife along side the straight edge and push down as you pull it all the way along the cut line. Recut the panel seven or eight times using the same method.
Set aside the straight edge and the utility knife. Move the acyclic panel to the edge of the table until the cut line hangs off by 1/4 to 1/2 inch.
Place one hand firmly on top of the acrylic panel. Grasp the overhanging edge with your other hand and snap it down firmly to break it off of the panel.