How the sand calculator works
Sand is measured out by volume but priced and carried by weight, and its weight changes a lot with the water it holds. The calculator first finds the volume of the space (length × width × depth), then adds an allowance that depends on the job: loose sand in a sandbox barely settles, screeded bedding sand is pressed down by the pavers and the plate compactor, and fill that is compacted in layers shrinks the most. Finally it multiplies by a bulk density for dry, damp or wet sand.
Weight = length × width × depth × job allowance × bulk densityDamp sand straight from a yard pile often weighs around 1,750 kg/m³ (about 2,950 lb per cubic yard), while dry bagged play sand is closer to 1,600 kg/m³ (100 lb/ft³). If you order by the tonne and the load arrives soaked after rain, you receive less sand for the same weight, so it pays to order dry-weather deliveries or a little extra.
Worked example
A sandbox of 2 m × 1.5 m filled 30 cm deep holds 2 × 1.5 × 0.30 = 0.90 m³. With the 5% sandbox allowance you need 0.945 m³, which is 945 litres. Dry play sand at 1,600 kg/m³ weighs 1,512 kg, so that is 61 bags of 25 kg, or about one bulk bag if your supplier delivers them. In imperial units a 6 × 5 ft box filled 12 in deep takes 31.5 ft³ with the allowance, about 1.17 yd³, 1.57 US tons, or 63 bags of 50 lb.
Types of sand and what they are for
| Sand | Grain | Typical use | Bulk density (dry–damp) |
|---|---|---|---|
| Play sand | Fine, washed, rounded | Sandboxes, play areas | 1,450–1,600 kg/m³ |
| Sharp or concrete sand | Coarse, angular, 0–4 mm | Paver bedding, concrete, screeds | 1,550–1,750 kg/m³ |
| Soft or building sand | Fine, with some clay | Bricklaying mortar, render | 1,500–1,700 kg/m³ |
| Kiln-dried jointing sand | Very fine, dry | Brushing into paver joints | 1,450–1,550 kg/m³ |
| Fill or bank sand | Mixed, unwashed | Levelling, backfill, under slabs | 1,600–1,900 kg/m³ |
For conversions: 1,600 kg/m³ equals about 1.35 US tons per cubic yard, and a US ton of damp sand fills roughly 0.7 cubic yards.
Getting the right sand for the job
- Sandboxes need washed play sand. Building sand contains clay that stains clothes and sets hard when wet. Leave 5–10 cm (2–4 in) below the rim so the sand stays in the box.
- Bedding sand should be sharp. Angular grains lock together under pavers; rounded play sand rolls and lets the surface sink. A bed of 3–5 cm (1–2 in) is normal; thicker beds creep and rut.
- Compact fill in layers. Lay 10–15 cm (4–6 in) at a time, dampen it and run a plate compactor over each layer; tipping it all in at once leaves soft spots that settle later.
- Keep deliveries covered. An open pile soaks up rain, gains weight and washes into drains. Store it on a sheet and under a tarp.
A reproducible calculation with complete inputs
For a reproducible sand calculator example, use the metric input system and enter Length: 2 m; Width: 1.5 m; Sand depth: 30 cm; What is the sand for?: Sandbox or play area (+5%); Sand condition: Dry, e.g. bagged play sand (1,600 kg/m³); Bag size: 25 kg bag. These settings describe one specific scenario, not a new default for every job. The result follows the method and allowances already explained above. Keep the entire set of values when comparing it with a hand calculation; omitting a selected material or an allowance can change the result even when the dimensions match. The following rows show the unrounded calculation values alongside the precision used by the interface.
| Result | Calculation value | Displayed value | Unit |
|---|---|---|---|
| Sand needed | 0.945 | 0.94 | m³ |
| Weight | 1.512 | 1.51 | t |
| Bags to buy | 61 | 61 | bags |
| Volume in litres | 945 | 945 | L |
| Area | 3 | 3.0 | m² |
How should I prepare these entries?
Length: enter the value in m. Width: enter the value in m. Sand depth: Sandbox 20–30 cm (8–12 in); paver bedding 3–5 cm (1–2 in); pipe or pool base 5–10 cm (2–4 in). What is the sand for?: choose among Sandbox or play area (+5%), Screeded bedding under pavers (+10%), Compacted fill or sub-base (+20%). Sand condition: choose among Dry, e.g. bagged play sand (1,600 kg/m³), Damp, as delivered from the yard (1,750 kg/m³), Wet or saturated (1,950 kg/m³). Bag size: choose among 25 kg bag, 20 kg bag, 50 lb bag. Choose the unit system before transferring your measurements. A depth, length, area and coverage can have different field units even within one system. Read each label individually rather than entering the same unit convention in every box. Optional openings or allowances should describe your actual scenario instead of being silently left at a sample value. The worked inputs above identify exactly which selections produced the table.
Frequently asked questions
How much sand do I need for a sandbox?
Multiply length × width × depth. A 4 × 4 ft box filled 12 in deep takes 16 ft³, about 1,600 lb of dry play sand or 32 bags of 50 lb.
How many bags of sand are in a tonne?
Forty 25 kg bags make one tonne. A US ton (2,000 lb) is 40 bags of 50 lb.
How much does a cubic metre of sand weigh?
Dry sand weighs about 1,600 kg per cubic metre, damp sand around 1,750 kg and saturated sand up to about 1,950 kg.
How much sand do I need under pavers?
Plan on 3–5 cm (1–2 in) of sharp sand. For 20 m² at 3 cm that is 0.6 m³, or 0.66 m³ with a 10% allowance, which weighs roughly 1.15 tonnes damp.
How many cubic feet are in a 50 lb bag of sand?
A 50 lb bag of dry play sand holds about 0.5 ft³, so a cubic yard takes about 54 bags.