Sand Calculator — Bags Needed for Paving, Levelling, or Play Areas
Sand is used as a paving base, a levelling layer, or a play-area fill. Because it is sold by weight, you need both the volume and the density to know how many bags to buy. This calculator does both in one step.
How we calculate
Volume = length × width × depth (m) × (1 + waste %). Weight = volume × density. Bags = ⌈weight ÷ bag weight⌉.
Worked example
4 m × 3 m at 40 mm: volume = 0.48 m³ × 1.1 = 0.528 m³. At 1,600 kg/m³: 845 kg. At 25 kg/bag: ⌈845 ÷ 25⌉ = 34 bags.
Common mistakes
- Using building sand where sharp (concreting) sand is needed — the grain shapes behave very differently.
- Not compacting the sand base before laying paving — loose sand causes slabs to rock and settle unevenly.
- Applying a sand layer that is too thick — a paving bed over 50 mm becomes unstable.
- Ordering bags for large areas — a bulk tonne bag is usually 30–50% cheaper per kg.
Frequently asked questions
How deep should the sand bed be under paving slabs?+
Use a 30–50 mm compacted sand bed under paving slabs. Too thin and slabs rock; too thick and they become unstable. The sand layer is in addition to any compacted hardcore base beneath it.
What type of sand should I use for paving?+
Use sharp (concreting) sand for a paving base — its angular grains compact well and resist movement. Do not use building (soft) sand, which is too fine and will wash out from under slabs over time.
How many bags of sand do I need per square metre?+
At 40 mm depth with a density of 1,600 kg/m³, one square metre needs about 64 kg — roughly 3 bags at 25 kg each. Use this calculator to adjust for your exact depth and area.
How much sand do I need for a sandpit?+
A 2 m × 2 m sandpit filled 200 mm deep needs about 0.88 m³ of sand — approximately 1,400 kg or 56 bags at 25 kg. Play sand is a finer, washed grade — specify this to your supplier rather than standard builder's sand.