Sketch a drawing of the couch on the first page, and label its parts. It's okay if the sketch is very basic. This helps make it easier to identify the parts on the subsequent pages.
Title each page with the parts of the couch. There should be one page dedicated to each part – the couch back, the seat cushions, the arms, the front, the sides, the outer back of the couch and the underside of the couch.
Sketch the first couch part at the top of the page. Carefully examine the shape of the couch section, and draw its outline on the paper. This drawing makes it an easy reference for the measurements later on. Do this for each part.
Reserve the space on each page for more information about each part. These pages will now be the reference guide for the couch parts as each piece is measured. Once the measurements of all the parts are recorded, estimating the amount of fabric needed to cover the couch will be easy.
Remove the seat cushions. Measure the width and length of the top surface of each seat cushion with a tape measure. Then, measure the width and length of each of the four sides of each seat cushion. Record these measurements in the notebook.
Measure the width and length of the seat. This is the couch surface hidden beneath the cushions.
Measure the couch's backrest. This is the back that's leaned on while sitting. Measure the bottom width of the back, the middle width and the top width of the back to equal three horizontal measurements. Next, measure the central height of the couch back and the height at two more locations on both sides of the back's center. This will equal five height measurements of the back. These measurements account for any contours in its design.
Measure the arms. Measure each arm from the inside seat area upward and around the couch arm, following the existing fabric to the seam just below the outer side of the arm. This is for the height. Then, measure the width of the arm from the backrest of the couch to the arm's edge. Record these measurements.
Measure the front of the couch. This includes the front part just below the seat and the two armrest fronts. Measure the width and length of each of these parts.
Measure the sides of the couch. Record the height and width of each side, just below the arm rest. Carry the measurement to each vertical edge.
Measure the back of the couch, recording its width and length.
Turn the couch on its side, and record the width and length of its underside. This piece of fabric stretched over the underside of the couch covers the lower edges of the fabric cover and encloses and finishes the couch from underneath.