Sandbox Calculator
How much play sand a sandbox needs at any fill depth — 50-lb bags of play sand, plus tons and yards for big boxes.
Play sand, by the bag
Sandboxes are filled by depth, not to the brim — the sand sits a few inches below the rim so it stays in the box instead of migrating across the yard. Play sand is sold washed and screened in 50 lb bags, and each bag holds about half a cubic foot, which is why a modest box eats bags by the dozen: the calculator counts the volume of your box at your fill depth and converts it to bags, with tons and yards alongside for big boxes where a bulk order makes sense.
Volume = length × width × fill depth · Bags = volume (with waste) ÷ 0.5 cu ft per 50 lb bag · Tons = volume × 100 lb per cu ft
Example: a 5 × 5 ft sandbox filled 8 in deep takes 16.7 cu ft of sand — with the allowance, 18.3 cu ft: 37 bags of play sand, or about 0.92 tons in bulk.
Only use bagged play sand (or bulk sand sold as play sand) in a sandbox: it is washed, so it does not stain clothes or skin, and screened free of the sharp grit in builder's sand. A cover is not optional equipment — it keeps the sand dry, leaf-free and unvisited by neighborhood cats, and dry sand is pourable sand, which is the whole fun of the box.
Frequently asked questions
How deep should the sand in a sandbox be?
6–8 in is the working depth for digging and molding; deeper than 10 in mostly buys weight and cost. Whatever depth you choose, leave 2–3 in of rim above the sand line to contain it — the calculator's depth is the sand depth, not the box depth.
Play sand vs regular sand — does it matter?
Yes. Play sand is washed and screened: it rinses off skin and clothes, packs smoothly for castles, and has no coarse sharp fraction. Builder's or fill sand is unwashed, stains, and can carry grit you do not want in small hands. For a sandbox, always the washed product.
How much does a bag of play sand cover?
A 50 lb bag holds about 0.5 cu ft — spread 8 in deep it covers only about 0.75 sq ft, which is why the bag counts surprise people. A 4 × 4 ft box at 8 in already needs over 20 bags; the calculator keeps the arithmetic honest before you reach the store.
How do I keep sandbox sand clean?
Cover the box whenever it is not in use — that single habit handles cats, leaves and rain. Rake the sand occasionally to surface anything buried, top up the level each season (sand compacts and escapes), and replace it fully every year or two in a well-used box.
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