A placemat can be any size but the most common sizes are 18" X 14", 18" X 16" and 16" X 14". If you don't know what size would be pleasing and what would fit for your table and place setting, I suggest you cut up a newspaper page to the three sizes above and try them on your table to see what you like. Once you decide your finished size, add 1" to the width and the length dimensions. This will give you 1/2" seam allowances around all four sides. Cut out two rectangles for each placemat and one batting piece. Put the placemats right sides together. Then pin the batting to one of the wrong sides. All three will be sewn together.