About the Sandbox Calculator
This tool estimates how much sand you need to fill a rectangular play sandbox, based on straightforward volume geometry. Enter the sandbox's length and width, the depth you want to fill it, and a waste allowance for settling and spillage — the calculator returns the volume in cubic feet and cubic yards, the estimated weight, and how many bags of sand to buy.
The formula
Sand volume is a rectangular-prism calculation: Volume = Length × Width × Depth. Length and width are measured in feet; depth is entered in inches and converted to feet (divide by 12) before multiplying. The raw volume in cubic feet is then increased by a waste/compaction allowance — typically 10% — to account for material lost during spreading, leveling, and normal settling after delivery.
Cubic feet convert to cubic yards (the unit bulk sand is usually sold in) by dividing by 27, since a cubic yard is 3 ft × 3 ft × 3 ft. Weight is estimated using a standard dry-sand density of approximately 100 pounds per cubic foot (about 2,700 pounds per cubic yard). Dividing the total weight by your chosen bag size and rounding up gives the number of bags to buy.
How to get the best results
- Measure length and width at the inside edges of the sandbox frame, not the outside.
- Use 12 inches (1 foot) as a common fill depth for children's play sand, or less for shallower boxes.
- Keep the waste allowance at 10% for a straightforward rectangular box; raise it if the box has an irregular shape or edging that eats into usable depth.
- For bulk (truck-delivered) sand, compare the cubic yard figure to your supplier's minimum order — many yards sell in half-yard increments.
Practical context
The calculator assumes a simple rectangular sandbox with a flat, level base. Actual sand needed can vary with sand moisture content, the shape of the box (round or irregular boxes need a different area formula), and how tightly the sand is packed on delivery. Treat the result as a solid planning estimate and round up when ordering, since running short mid-project usually costs more than a small surplus.