Theoretically, it takes the same amount of fabric for a straight cut binding as for a bias cut binding.
Length times width equals area.
However - that does not factor in fabric lost/wasted in joins or matching a design if that is important.
When I can, I cut from selvage to selvage and usually have a couple of big triangles left over. But if a lot of seams don't bother you and you are trying to squeak by with as little fabric as possible, theoretically, 1/2 yard of 40 inch usable width would do it. I would go with an absolute minimum of 5/8 yard (if available) and preferably 3/4 yard.
If it was me - and I had the money and the fabric was available - I would go with 1-1/4 yards.
240 x 2.5 = 600 inches
600 / 40 = 15 inches
That would be the length of 40 inch wide fabric to cover 600 inches of area.
That does not take into account joins, pattern matching, or cutting errors.