# Sandbox Sand Calculator

URL: https://speedycalculator.com/calculators/other/sandbox/
Last updated: 2026-10-30

> The sandbox calculator works out how much play sand you need for a round, rectangular, pentagonal, hexagonal or custom-shaped sandbox, with a fill depth suggested by the child's age – in cubic feet or cubic metres, pounds or kilograms, and the number of bags to buy.

## Inputs

- Sandbox shape
- Radius (ft, m, in, cm)
- Length (ft, m, in, cm)
- Width (ft, m, in, cm)
- Side length (ft, m, in, cm)
- Area (ft², m², in², cm²)
- Child's age (suggested sand depth)
- Sand depth (in, cm, ft, m)
- Sand density (dry play sand ≈ 1,600 kg/m³) (kg/m³, lb/ft³, g/cm³)
- Extra for settling and spills (%)
- Bag size (lb, kg, t (metric), short ton)
- Price per bag

## Results

- Sandbox area
- Sand depth
- Sand volume (incl. extra)
- Sand weight
- Bags of sand to buy
- Cost of sand

## 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⌉
```

## Explanation

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

AgeSand depth1–2 years4 in (10 cm)2–3 years6 in (15 cm)3–5 years8 in (20 cm)5–12 years12 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

FieldWhat to enterSandbox shapeChoose one: Round, Rectangular or square, Pentagon (5 equal sides), Hexagon (6 equal sides) …RadiusUnits: ft, m, in, cmLengthUnits: ft, m, in, cmWidthUnits: ft, m, in, cmSide lengthUnits: ft, m, in, cmAreaUnits: ft², m², in², cm²Child'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 depthUnits: in, cm, ft, mSand density (dry play sand ≈ 1,600 kg/m³)Units: kg/m³, lb/ft³, g/cm³Extra for settling and spillsIn %Bag sizeUnits: lb, kg, t (metric), short tonPrice per bagAmount 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]

## 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.

## FAQ

**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.


## Sources

- [U.S. CPSC – Public Playground Safety Handbook](https://www.cpsc.gov/s3fs-public/325.pdf)
- [Wikipedia – Bulk density (typical values for sand)](https://en.wikipedia.org/wiki/Bulk_density)