Hi Jerry,

That is a very difficult question to answer with mathematics alone. Volume has three dimensions (length, width and height) and we do not know how far the bag will expand when it is filled to 60% capacity with sand. The way you can determine how much sand you need is to fill one bag to the desired capacity and then multiply by 750 to determine the total amount needed. Remember that two bags that have the exact same dimensions but made of different material will expand in different ways so volume can only be determined experimentally.

Hope this helps,

Janice