Sand Calculator
Work out how much sand you need for paving, mortar, concreting or levelling – in cubic metres, tonnes and 25 kg bags, with the cost in GBP.
Formulas shown on this page · Last reviewed October 2026
How the sand calculator works
volume (m³) = area (m²) × depth (mm) ÷ 1,000
tonnes = volume × (1 + waste) × density (t/m³)
bags = tonnes × 1,000 ÷ bag size (kg)
Sand density is approximate: about 1.5 t/m³ for soft sand and 1.6–1.7 t/m³ for sharp or bedding sand, and damp sand is heavier than dry. Edit the density above if your supplier gives a figure.
Types of sand and where they are used
| Type | Approx. density | Typical depth |
|---|---|---|
| Building sand (soft) | 1.5 t/m³ | Mixed into mortar |
| Sharp sand (concreting) | 1.6 t/m³ | Mixed into concrete or screed |
| Paving / laying course sand | 1.6 t/m³ | 25–50 mm bedding layer |
Soft building sand is for bricklaying mortar and render; sharp sand is for concrete, screed and bedding slabs; jointing sand fills the gaps between paving.
Buying sand in the UK
Merchants sell 25 kg bags and bulk bags of about 850 kg, plus loose sand by the tonne for larger deliveries. Sand stored outdoors soaks up rain and weighs more, so keep bags under cover or buy slightly more by weight than you calculate.
At the default prices, a 25 kg bag costs £4.00, which works out to about £160 per tonne in bags, compared with roughly £48 per tonne loose. Bulk is far cheaper per tonne once you need more than around half a tonne. These are typical prices – check your local supplier.
Frequently asked questions
How much sand do I need for a 4 × 3 m area at 50 mm deep?
The base volume is 0.6 m³. With 10% extra that is 0.66 m³, or about 0.99 tonnes at 1.5 t/m³.
How many 25 kg bags is that?
0.99 tonnes is 990 kg, which needs 40 bags of 25 kg (rounded up) – about £160 at the default price.
How many tonnes of sand are in a cubic metre?
Around 1.5–1.7 tonnes, depending on the type and moisture. One cubic metre of building sand (soft) is about 1.5 tonnes.
What sand should I use under paving?
Use a coarse, sharp or dedicated bedding sand, levelled to about 25–50 mm and compacted. Soft mortar sand is too fine and can wash out.