To determine if a couch cover will fit your sofa, you'll need to measure your couch accurately. First, measure the length of your couch from one outer edge to the other. This should include the arms if your couch has them. Then, measure the depth, from the back of the couch to the front. Lastly, measure the height, from the bottom of the couch to the top of the backrest. Once you have these dimensions, compare them with the specifications provided by the couch cover manufacturer. The cover's dimensions should be slightly larger than your couch's measurements to ensure a snug fit. Remember, it's always better to choose a cover that's a bit larger than your couch than one that's too small. It's also important to consider the shape and style of your couch, as some covers are specifically designed for certain types of sofas. Always read the product description and reviews to ensure the cover will accommodate your specific couch style.