Our calculations are based on a following fact:  A standard 14" x 26" (36 by 66 cm) sandbag or 17" x 32" (43 by 81 cm) sandbag can hold around 50 pounds of sand. In order to calculate the number of bags for your sandbox, use the following formula:
No. of bags = Amount fo sand needed (lb) / 50
Yay, that definitely was an easy job!  Read more