Measure and record the length of the sofa at the widest width. This is probably from one arm to the other.
Measure and record the back of the sofa from top to bottom at the highest point .
Measure the cushions from one end to the other. This is especially important if you are buying a slipcover that has separate covers for the cushions.
Measure and record the front of the sofa from top to bottom.
When choosing a slipcover, choose the smallest size that will work. A tight fitting slipcover looks best. Also look for slipcovers with ties around the edges. This improves the look and fit of the slipcover.