How to work out sandbox sand
bags of play sand (50 lb) = length × width × depth (ft) × 2
That shortcut works because a 50 lb bag of dry sand is about half a cubic foot. The calculator does it more exactly by weight and adds a settling allowance.
Worked example. A 5 × 5 ft box, sand 8 inches deep:
- 5 × 5 = 25 sq ft
- 8 inches = 0.667 ft, so 25 × 0.667 = 16.7 cubic feet
- Plus 10% for settling: 18.3 cubic feet (0.68 cubic yards)
- At about 100 lb per cubic foot: about 1,833 lb
- 1,833 ÷ 50 = 36.7, so 37 bags
Measure the inside of the box, not the outside of the boards. On a 4 × 4 ft kit with 2-inch thick boards, the inside might be closer to 3.7 × 3.7 ft, about 15% less sand.
Sandbox sand chart
Bags of 50 lb play sand, including 10% for settling. Round up.
| Inside size | 6 in deep | 8 in deep | 10 in deep | 12 in deep |
|---|---|---|---|---|
| 3 × 3 ft | 10 bags | 14 bags | 17 bags | 20 bags |
| 4 × 4 ft | 18 bags | 24 bags | 30 bags | 36 bags |
| 5 × 5 ft | 28 bags | 37 bags | 46 bags | 55 bags |
| 6 × 6 ft | 40 bags | 53 bags | 66 bags | 80 bags |
| 8 × 8 ft | 71 bags | 94 bags | 118 bags | 141 bags |
| 6 ft round | 32 bags | 42 bags | 52 bags | 63 bags |
Once you are past about 50 bags, you are into cubic-yard territory, and a bulk delivery may be worth pricing. The calculator shows cubic yards too.
How deep should a sandbox be?
Most home sandboxes are filled with roughly 6 to 12 inches of sand:
- 6 inches is enough for toddlers patting and pouring.
- 8 to 12 inches gives older kids room to dig holes and build without hitting the bottom.
- Leave a few inches of wall above the sand so it stays in the box.
A layer of landscape fabric under the sand stops it mixing with the dirt below while still letting rain drain. A cover keeps out leaves and animals.
Play sand vs other sand
- Play sand is washed and screened to remove clay, silt and debris, and is usually sold in 50 lb bags labelled for children’s play.
- Mason sand is also fine and washed and is sold in bulk, which can make it cheaper for big boxes. See mason sand vs play sand.
- Fill sand and concrete sand are coarser and may contain small stones or silt. They are not made for play.
If dust is a concern, choose sand labelled for play and keep it slightly damp; wet sand makes far less dust. Read the bag and ask the supplier if you have questions about what is in it.
Topping up
Sand slowly leaves a sandbox on shoes, clothes and toys. To top up, measure the depth you have lost at a few points, average it, and run the calculator for just that depth. Losing 2 inches from a 5 × 5 ft box is about 4.2 cubic feet, or 10 bags with the 10% allowance.
Bag counts assume dry sand at about 100 lb per cubic foot. Bags of damp sand hold a little less, so buy one or two extra and keep the receipt.
Questions people ask
- How much play sand do I need for a sandbox?
- Multiply the inside length × width of the box in feet by the sand depth in feet to get cubic feet. Each 50 lb bag of play sand holds about half a cubic foot, so double the cubic feet to get bags. A 5 × 5 ft box filled 8 inches deep needs about 37 bags including 10 percent for settling.
- How deep should sand be in a sandbox?
- Most backyard sandboxes hold roughly 6 to 12 inches of sand. Leave a few inches of box wall above the sand to keep it in.
- How many bags of play sand are in a cubic yard?
- About 54 bags of 50 lb, since a cubic yard of dry sand weighs about 2,700 lb.
- Is it cheaper to buy play sand in bags or in bulk?
- For a small box, bags are usually simplest. For larger boxes needing a cubic yard or more, a bulk delivery of washed sand can cost less, but compare a local delivered price with the bag price first.
- Can I use mason sand in a sandbox?
- Many people do, because mason sand is fine and soft. Make sure it is washed and screened, and look at it before buying. Bagged sand labelled for play is the simplest choice.