Advanced options
Use certified PLAY sand only: builders' sand stains clothes and skin and isn't washed or safety-graded. 10-15cm depth suits digging without emptying the budget; a third to half fill of a deep pit is normal. A cover is non-negotiable (cats), and drainage holes or a base membrane stop the swamp.
What The Sandpit Sand Calculator Works Out
- Sand volume: length x width x depth, converted to litres. A 120cm x 120cm pit filled to 15cm holds 216 litres, which is why the sandpit-assembly ritual usually includes a second trip to the shop.
- Sand needed: the volume multiplied by the density of dry play sand (about 1.5kg per litre), then divided into 25kg bags. The same 120cm pit needs around 324kg, or 13 bags.
- Round pit: a quick comparison for a circular pit of the same diameter and depth. A circle covers about 79% of the square it sits in, so the round version needs roughly a fifth less sand.
- Depth guidance: 10cm to 15cm is enough for castle-and-bury play; filling a deep moulded pit to the brim adds cost and weight without play value. Manufacturers quietly assume a third-to-half fill.
- Pit shape (advanced): switch between rectangle, round (length is the diameter) and hexagon (length is the corner-to-corner width) so the footprint matches the pit you actually own.
- Sand density (advanced): dry play sand is about 1.5kg per litre, damp sand nearer 1.7kg. Edit it if the bag states a different figure.
- Bag size and top-up allowance (advanced): play sand comes in 15kg, 20kg and 25kg bags; a bulk bag is about 800kg. The top-up allowance adds a percentage for the sand that leaves on shoes and in buckets over a season, and the card shows how much is left spare after rounding up.
- Estimated cost (advanced): bags to buy multiplied by your price per bag. Certified play sand typically costs GBP 4 to GBP 8 per 25kg; builders' sand is cheaper but stains and is not safety graded.
- Fill level (advanced): enter the internal height of the pit to see what percentage of it the sand fills. Above about 60% full, sand ends up over the edge as soon as digging starts.
- Depth table (advanced): the weight, bags and cost at 5cm to 30cm so you can trade depth against budget before buying.