The formula and two worked examples
The math is the same whether your area is a rectangle or a circle — only how you get the square footage changes:
Cubic feet = Area (sq ft) × (Depth in ÷ 12) × (1 + waste %)
Cubic yards = Cubic feet ÷ 27
Tons = Cubic yards × material density (tons per cubic yard)
Rectangular example: a 5 ft × 5 ft sandbox, filled 6 inches deep, with the default 5% waste allowance and dry play sand (1.35 tons/yd³):
5 × 5 × (6 ÷ 12) = 12.5 ft³
12.5 × 1.05 ≈ 13.13 ft³ → 13.13 ÷ 27 ≈ 0.49 yd³
0.49 × 1.35 ≈ 0.66 tons ≈ 27 bags of 50 lb
Circular example: a round sandbox 6 ft in diameter (radius 3 ft), also filled 6 inches deep:
π × 3² ≈ 28.27 sq ft, × (6 ÷ 12) = 14.14 ft³
14.14 × 1.05 ≈ 14.84 ft³ → 14.84 ÷ 27 ≈ 0.55 yd³
0.55 × 1.35 ≈ 0.74 tons ≈ 30 bags of 50 lb
Dividing by 27 converts cubic feet to cubic yards, since a cubic yard is 3 ft × 3 ft × 3 ft = 27 cubic feet — the unit sand is typically priced and delivered by, along with weight in tons.
What a yard of sand actually weighs
Dry sand weighs about 2,700 pounds per cubic yard (1.35 tons) — that's the default this calculator uses. Wet sand weighs noticeably more for the exact same volume, since the water adds weight without adding bulk; depending on how saturated it is, wet sand can run 3,000 pounds or more per cubic yard.
Because weight shifts with moisture, it's worth buying and measuring sand by volume(cubic yards or cubic feet) whenever you have the choice, rather than assuming a fixed weight-per-yard figure. If a supplier only sells by the ton, ask whether their sand is dry or wet — it changes how much volume you're actually getting for that weight.
Play sand vs. fill sand vs. masonry sand
Not all sand is interchangeable, and using the wrong type can cause real problems:
- Play sandis washed and screened specifically for sandboxes — it's free of dust and sharp debris and has rounded grains that are soft to dig in and touch. This is what kids should be playing in.
- Fill sandis a cheaper, coarser, unwashed sand used for filling holes, low spots, and leveling ground before sod, pavers, or a structure goes in. It's not intended for play or for mixing into mortar.
- Masonry sand is washed and fine-graded for mixing into mortar and stucco, where a consistent, workable texture matters for the finished mix.
One product this calculator doesn't cover is the sand that goes under patio pavers. Paver bedding uses a coarser, angular concrete sand — a different material chosen because it locks together under compaction instead of staying loose like play sand does. If that's your project, use our paver sand & base calculator instead, which sizes the bedding sand and gravel base layer together.
How deep should a sandbox be filled
6 to 8 inchesis the typical depth for a play sandbox. That's deep enough for digging, molding, and building without the bottom showing through as sand gets pushed around during play, but not so deep that you're paying for sand that never really gets used.
For fill or leveling jobs rather than a sandbox, depth depends entirely on how much space you're filling — measure the gap or low spot directly rather than using a rule of thumb.