If you are having them made for you, the upholsterer will tell you the yardage, based on the fabric you choose. It depends on the following:

Measurements of the cushions
Type of finishing (ex self binding)
Width of fabric
special cuts (like mitered corners)
If the fabric has a nap (direction of texture)
If the fabric is patterned, what are the repeats and does it need to be in the same direction or matched

Look at this fabric yardage chart...first one in the forth row. Looks to be a small banquette (maybe 60" x 30"?) requiring 7 yards. Your 7 foot x 5 foot would need a bit more. These are estimates only. Sarah makes good points you should consider.

DIYupholstery - Yardage Estimator

Thanks, I'm just trying to get ahead of the game and get the fabric lined up.

Yes, exactly as Sarah said, plus whether or not the fabric can be railroaded, and an amount needed for welting.