Sand Calculator
Works out sand for a paving bed, a sandpit or a mix. Gives tonnes and cubic yards along with bulk and retail bags.
Includes the waste allowance — this is the figure to order.
Share sends a link that reopens these numbers. Copy details pastes the full breakdown as a list.
The formula
volume = length × width × depth × (1 + waste) weight = volume × bulk density
The geometry is trivial; the bulk density is where the answer actually comes from. Sand runs about 1600 kg per cubic metre loose, so a cubic metre weighs roughly 1.60 tonnes. Suppliers quote one or the other, which is why both are given.
What to watch out for
The type matters more than the quantity:
- Sharp sand — gritty and angular. For laying slabs, screeding and concrete.
- Building sand — soft and fine. For mortar. It will not do as a paving bed; it holds water and moves.
- Kiln-dried sand — for brushing into block paving joints only.
A paving bed is 25–50 mm screeded level and left uncompacted until the slabs are down. Any deeper and the slabs settle unevenly as the sand consolidates under load.
Frequently Asked Questions
How much sand do I need for a patio?
Allow 25–50 mm of sharp sand under the slabs. A 5 × 3 m patio at 40 mm needs 0.6 m³, close to a tonne once waste is added.
How much does a cubic metre of sand weigh?
About 1.6 tonnes dry. Wet sand is heavier — up to 1.9 tonnes — which matters when a yard sells by weight and you have measured by volume.
What sand should I use under paving?
Sharp sand, not building sand. Sharp sand drains and stays put under load; soft building sand holds water and lets slabs rock and settle.