Play sand is sold by weight in bags, but a sandbox is measured in length, width and depth – so the job is to turn a shape into a volume and the volume into a number of bags. Washed and screened play sand weighs roughly 1,600 kg per cubic metre (about 100 lb per cubic foot) when dry, a little more when damp, so even a small box takes a surprising amount.
How deep to fill depends on who will play in it. Toddlers are happy with a few inches they can scoop and pour, while older children want enough depth to dig holes, build castles and bury toys. Leave a few inches of the wall above the sand so it stays in the box, and add about 10% for settling and the sand that inevitably leaves on shoes and clothes.
The calculator handles the common shapes of ready-made and DIY sandboxes and anything else via a custom area, and lets you change the bag size and price to match your store.
How to use the Sandbox Sand Calculator
- Sandbox shape
- Radius
- Length
- Width
- Side length
- Area
- Child’s age (suggested sand depth)
- Sand depth
- Sand density (dry play sand ≈ 1,600 kg/m³)
- Extra for settling and spills
- Bag size
- Price per bag
Results update as you type, every field has its own unit menu, and everything is calculated in your browser.
How it works
Pick the shape and enter its dimensions, choose the child’s age group (or a custom depth) and set the sand density, bag size and extra allowance. The area times the depth gives the volume; the density converts it to weight; dividing by the bag weight and rounding up gives the bags.
Worked example
A 4 × 4 ft sandbox for a 4-year-old, filled 8 in deep: 16 ft² × 0.667 ft = 10.67 ft³ (0.302 m³). Adding 10% gives 11.73 ft³ (0.332 m³). At 1,600 kg/m³ that is 532 kg, or 1,172 lb – 23.4 bags of 50 lb, so buy 24 bags (about $156 at $6.50 a bag).
Suggested depths
| Age | Sand depth |
|---|---|
| 1–2 years | 4 in (10 cm) |
| 2–3 years | 6 in (15 cm) |
| 3–5 years | 8 in (20 cm) |
| 5–12 years | 12 in (30 cm) |
These are practical suggestions for play depth, not a safety standard. Keep 2–4 in of wall above the sand.
Inputs explained
| Field | What to enter |
|---|---|
| Sandbox shape | Choose one: Round, Rectangular or square, Pentagon (5 equal sides), Hexagon (6 equal sides) … |
| Radius | Units: ft, m, in, cm |
| Length | Units: ft, m, in, cm |
| Width | Units: ft, m, in, cm |
| Side length | Units: ft, m, in, cm |
| Area | Units: ft², m², in², cm² |
| Child’s age (suggested sand depth) | Choose one: 1–2 years – 4 in (10 cm), 2–3 years – 6 in (15 cm), 3–5 years – 8 in (20 cm), 5–12 years – 12 in (30 cm) … |
| Sand depth | Units: in, cm, ft, m |
| Sand density (dry play sand ≈ 1,600 kg/m³) | Units: kg/m³, lb/ft³, g/cm³ |
| Extra for settling and spills | In % |
| Bag size | Units: lb, kg, t (metric), short ton |
| Price per bag | Amount in your currency |
What each result means
- Sand volume (incl. extra) = [Sandbox area]×[Sand depth]×(1 + [Extra for settling and spills]÷100)
- Sand weight = [Sand volume (incl. extra)]×[Sand density (dry play sand ≈ 1,600 kg÷m³)]
- Bags of sand to buy = ceil([Sand weight]÷[Bag size] – 1e-9)
- Cost of sand = [Bags of sand to buy]×[Price per bag]
Formula
Volume = area × depth × (1 + extra %) · round: area = π r² · rectangle: a × b · pentagon: ¼√(5(5 + 2√5)) a² ≈ 1.7205 a² · hexagon: (3√3 ÷ 2) a² ≈ 2.5981 a² · weight = volume × density · bags = ⌈weight ÷ bag size⌉
Worked example
Inputs — Sandbox shape: Rectangular or square; Length: 4 ft; Width: 4 ft; Child's age (suggested sand depth): 3–5 years – 8 in (20 cm); Sand density (dry play sand ≈ 1,600 kg/m³): 1,600 kg/m³; Extra for settling and spills: 10 %; Bag size: 50 lb; Price per bag: $6.5.
Results — Sandbox area = 16 ft²; Sand depth = 8 in; Sand volume (incl. extra) = 11.7333 ft³; Sand weight = 1,171.9809 lb; Bags of sand to buy = 24; Cost of sand = $156.00.
Key terms
- Play sand
- Washed and screened fine sand sold for children's play.
- Bulk density
- Mass of loose sand per unit volume, including air between the grains.
- Settling allowance
- Extra sand to make up for compaction and losses.
Frequently asked questions
How much sand do I need for a 4 × 4 ft sandbox?
At 8 inches deep: 4 × 4 × 0.667 = 10.7 ft³, about 1,070 lb of dry play sand – with 10% extra, 24 bags of 50 lb.
How deep should sand be in a sandbox?
4–6 inches for toddlers and 8–12 inches for older children, leaving a few inches of wall above the sand.
How much does play sand weigh?
About 100 lb per cubic foot (1,600 kg/m³) when dry; damp sand is heavier, up to about 120 lb/ft³.
How many 50 lb bags are in a cubic yard?
A cubic yard of dry sand weighs about 2,700 lb, so roughly 54 bags of 50 lb.
What kind of sand should I use?
Washed, screened play sand sold for sandboxes. Avoid construction sand with sharp grains or silt, and sand with high crystalline-silica dust.
How do I calculate a hexagonal sandbox?
Area = 2.598 × side². A hexagon with 2.5 ft sides has 16.2 ft²; at 8 in deep that is 10.8 ft³.