You'll need to measure and record the length and width of each section of the love seat. If the back of the seating area has two sections, measure each separately. Measure each seat cushion, including length, width and height. Measure height and width of front and back frames and sides. Most love seats typically require at least 10 yards of fabric to complete the upholstery.
The design of the fabric also plays an important role in how much you will need. If there is a pattern, you will have to factor in the repeat, which is the length and width of the design as it appears in one section of fabric. In order to make the upholstery line up and be visually correct, you will need to purchase additional fabric to compensate. If your love seat has a ruffle or skirting around the bottom, you'll also need at least two to three additional yards to create this feature. Piping will require at least one to two yards. For each section measured, always add one to two inches per section for seam allowances. If you are doing the project yourself, you may also want a few extra yards for mistakes.
If you are uncertain of how to proceed, take front, side and back pictures of the love seat. Take the measurements as accurately as possible, then take these items with you to the fabric store or upholstery shop. They can then assist you in determining the exact amount needed for the piece, including repeats, skirting and piping.