Well, gee, I think that would be 2 bags. But if you have found a bag that is 2 cubic yards, that is ONE HUGE BAG...Enough to fill the back of a pick-up truck. I think you better look into your phrasing, one cubic yard of mulch will cover 100 square feet, or an area that is 10' x 10'.
IMPROVED ANSWER: I think you mean that 1 bag of mulch will cover 2 cubic feet. That's the standard bag sold at Lowes & Home Depot. 1 cubic yard = 27 cubic feet (3'x3'x3'=27). Therefore 4 cubic yards is equal to 108 cubic feet. You would need 54 bags (108/2=54).
That's 13 cubic yards of mulch for every 2 inches deep.
It depends how deep you want it.
The area covered by one cubic yard of Mulch is dependant on the depth that themulch is applied. At 3" it covers 108 ft2, at one inch it covers over 300 ft2.The 'square feet' of area that it covers is 324/(depth of the mulch, in inches)
1 cubic yard will cover ~90 sq feet
The 'square feet' of area that it covers is 1,620/(depth of the mulch, in inches)
One cubic yard of mulch will cover approximately 160 square feet at 2" deep, so you would need approximately two cubic yards of mulch to cover 271 square feet at 2" deep.
One cubic yard will cover a 324 square-foot area with one inch of mulch. However your mulch should be 2 to 3 inches thick to maintain moisture and prevent weed growth. Be careful not to go to thick or you will cause mold to form in the mulch.
201.6 cubic ft
1 cubic yard will cover 15 square yards at 3 inches deep.
5inches
It depends on how deep you want to lay it.
It depends on how thick the mulch is applied. For example, if applied at an average depth of two inches, the cubic yard of mulch will cover 162 square feet. If applied at an average depth of four inches, half that area or 81 square feet, etc.