How much concrete to order? If I make 4 of these statues, 1.25x life-size, then how much concrete should I purchase?

The plan is to make a mould and pour into that.


  The original Ludovisi Ares is 1.56 m in height. Therefore: (x1.25) 1.95 m high.


Update: I need to know how much Portland Cement (White), how much sand, and how much aggregate to order, and need a suggested recipe for the proportions of each and size(s) of aggregate I should use.

It has to be liquid enough to pour into a mould and take the shape, but strong enough after drying to stand in public and withstand subtropical temperates and humidity, heavy rain, strong winds, and cold temperates (rarely freezing, 0℃ only one day a year if even that). 

Finally, I will cure it for a full 28 or 30 days, and want it to have as smooth a finish ad possible.

Any and all advice would be appreciated. Thanks.
If each statue is 1.25x as large as the original, its volume will be 1.25 cubed, or a little over 1.95 times the volume of the original. If you can find out the weight of the original and the specific gravity of the stone of which it is carved, you can calculate the volume of stone in the statue and use that to calculate how much concrete you would need for a statue having almost twice the volume. I'll defer to the concrete experts about particulars on that subject.