When making or purchasing a table runner for your dining table, you should first determine the proper size of the table runner for your specific table. Table runners are not "one size fits all". Keep in mind that a table runner will fit your dining table differently with or without your table leaf, so you may need two different sized table runners. Table runner dimensions are approximate, so feel free to adjust the dimensions to suit your needs.
Some people only use table runners as decoration when the table is not being used. Others use table runners with placemats during dinner parties. Table runners can be used with or without a table cloth underneath. Consider getting a reversible table runner with a different fabric on either side (perhaps one side for fall and the other side for spring or one side for everyday and the other side for Christmas).
A table runner should be approximately 1/3 the width of your dining table. If your dining table is 48 inches wide, the table runner should be approximately 16 inches wide. If you plan on keeping the table runner on the table while dining, make sure there is plenty of room for a dinner plate without it being partially on the table and partially on the table runner.
A table runner should overhang the end of your table approximately 6 to 10 inches on each end. If your table is 72 inches long, the table runner should be 84 to 92 inches long. There can also be a tassel attached to the end making the overall length of the table runner longer.