A cubic yard of gravel could never be put into a bag, since it weighs around 2700 pounds. Five cubic yards would be 13,500 pounds.

Perhaps you need to know "How many 1/5th cubic foot bags make 1 cubic yard?" (Gravel is about 100 pounds per cubic foot so I'll assume a bag of 20 pounds). 27 cubic feet make 1 cubic yard. If your gravel comes in one fifth cubic foot bags, then you need 5 * 27 of them which is 135 bags (and a strong back with a good truck).

For 0.5 cubic foot bags, you would need 2 * 27 of them which is 54 bags (and they're 50 pounds per bag, and the load will still be 2700 pounds!)

You're probably better off going to a construction/building materials yard and buy it by the front-end-loader scoop. I think I paid about $60/yd for enough "1 inch minus" gravel to fill a pick-up truck.

Perhaps you need to know "How many 1/5th cubic foot bags make 1 cubic yard?" (Gravel is about 100 pounds per cubic foot so I'll assume a bag of 20 pounds). 27 cubic feet make 1 cubic yard. If your gravel comes in one fifth cubic foot bags, then you need 5 * 27 of them which is 135 bags (and a strong back with a good truck).

For 0.5 cubic foot bags, you would need 2 * 27 of them which is 54 bags (and they're 50 pounds per bag, and the load will still be 2700 pounds!)

You're probably better off going to a construction/building materials yard and buy it by the front-end-loader scoop. I think I paid about $60/yd for enough "1 inch minus" gravel to fill a pick-up truck.