The biggest problem with making a round tablecloth is finding fabric wide enough. Some quilting and bedding fabrics come in very wide widths, but most home sewing people have limited access to these specialty fabrics and may be choosing fabrics that are 45 to 60 inches wide. This means that you will need to seam your fabrics together to create the right width for very large tablecloths that are up to 120 inches wide.
Wash your fabric to remove the sizing and iron it.
Cut the fabric into three pieces of the same length. Each should be 10 feet, 4 inches long. Cut off the selvage edges of each section. The selvage is the edge of the fabric that is woven to prevent fraying. The selvage sometimes has names or other marks printed along the edge.
Place two pieces of the fabric, face sides together and seam them with a 1/2-inch hem. Place the remaining piece, face sides together with either side of the joined piece and seam them together with a 1/2-inch hem. Your seams should be parallel.
Fold the fabric in half lengthwise with face sides together. Fold the fabric in half widthwise. Locate the corner with folds on each side. This corner is the center of the fabric. Make sure the fabric is lined up and straight on the table.
Cut a piece of string 64 inches long. Tie one end of the string around a marker. Have a second person hold the other end of the string against the corner that is the center of the folded fabric. With the cap on the marker, drag the marker along the fabric edges. Locate the shortest section of fabric, which should be about 61 inches from the corner that is the center. Have the second person shorten the string to this length, uncap the marker and draw the arc on the fabric.
Holding the fabric in place, cut through all four layers of fabric along the line. This will create a perfect circle. Turn the hem under 1/2 an inch and sew the hem all around the tablecloth.