How Much Sand for a Sandbox?
Updated 2026-08-31 · Yardly
For a rectangular sandbox, you need length × width × depth of play sand — a 4×4 ft box filled 6 inches deep takes about 8 cubic feet (roughly 0.3 cubic yard, or 16 fifty-pound bags). Get the volume first, then decide bags versus bulk.
The sandbox sand formula
Sand is usually sold by the bag in cubic feet, but boxes are measured in feet and inches. Convert with the same volume math every Yardly calculator uses:
(Length × Width × Depth in feet) = cubic feet; ÷ 27 = cubic yards
For a sandbox, work in inches first, then divide by 12 to get feet. A 4 ft by 4 ft box at 6 inches deep is 4 × 4 × (6 ÷ 12) = 8 cubic feet, or about 0.30 cubic yards.
A worked example
| Box size | Depth | Cubic feet | Cubic yards |
|---|---|---|---|
| 4 × 4 ft | 6 in | 8 cu ft | 0.30 yd³ |
| 5 × 5 ft | 6 in | 12.5 cu ft | 0.46 yd³ |
| 6 × 6 ft | 6 in | 18 cu ft | 0.67 yd³ |
If you buy bags, a typical 50-lb play sand bag holds about 0.5 cubic foot. The 4×4 box (8 cu ft) is 16 bags; the 6×6 box (18 cu ft) is 36 bags. Once you are past roughly one cubic yard, bulk delivery by the yard is usually cheaper per cubic foot and saves a lot of lugging.
Pick the right depth
Four to six inches is the sweet spot for play. Less than 4 inches and kids hit the liner; more than 6 inches adds cost without adding fun. If your box has a hard bottom, 4 inches is plenty. If it sits on the ground, 6 inches feels better underfoot.
A drainage layer underneath
A shallow gravel layer below the sand keeps the box from pooling after rain. That is a separate estimate — our gravel calculator sizes a 1- to 2-inch bottom layer, and our fill dirt calculator helps if you are leveling the ground the box sits on first.
Safe-play basics
Use washed, screened play sand, not construction or sharp sand. Keep the lid on or a tarp over the box when it is not in use so animals stay out and the sand stays dry. Dampen the sand lightly before play to keep dust down, and refresh the top layer every year or two. QUIKRETE’s play sand guidance covers graded, washed options for children’s sandboxes.
Keep reading
- Sand calculator — estimate sand for any project by area and depth
- Gravel calculator — size a drainage layer under the box
- Fill dirt calculator — level the spot before you set the box down
Frequently asked questions
How deep should sandbox sand be?
Aim for 4 to 6 inches of sand. That is deep enough to dig, bury toys, and mold castles without hitting the bottom, while staying a reasonable volume to buy and refresh.
Is play sand safe for kids?
Use washed, screened play sand. The U.S. Consumer Product Safety Commission has found crystalline silica in ordinary play sand is not a hazard to children playing in a sandbox; keep the box covered when not in use and dampen the sand to cut dust. See CPSC guidance at https://www.cpsc.gov/.
How many 50-pound bags of sand fill a sandbox?
A 50-lb bag of play sand is roughly 0.5 cubic foot. Divide your total cubic feet by 0.5. A 4×4 ft sandbox at 6 inches deep needs about 8 cubic feet, or around 16 bags.