What this calculator does
A sand calculator turns an area and a depth into the volume of sand needed to fill it, and then, because sand is bought by weight, into tonnes and a bag count. The step that trips people up is the conversion from volume to weight: it depends on the density of the specific sand, which varies with the type and how damp or compacted it is, typically somewhere around 1.3 to 1.7 tonnes per cubic metre.
This calculator works out how much sand is needed for a given area and depth, in cubic metres, kilograms and tonnes, using a sand density you set yourself, plus an estimated bag count and cost. Check the density figure quoted by your supplier, or printed on the bag, rather than assuming a single fixed number applies to every kind of sand.
The formula
Volume is length times width times depth, with depth converted from millimetres to metres. That volume, in cubic metres, is multiplied by the density to give weight in tonnes, which is then converted to kilograms and divided by the bag size to estimate how many bags are needed.
| Term | Meaning |
|---|---|
| Density | How much a cubic metre of the sand weighs, in tonnes per cubic metre; varies with the sand type and moisture. |
| Volume | The space the sand needs to fill: area times depth, in cubic metres. |
| Bags needed | Total weight divided by the bag size, rounded up to a whole number of bags. |
The inputs explained
| Field | What to enter |
|---|---|
| Area length (m) | The length of the area to be covered. |
| Area width (m) | The width of the area to be covered. |
| Depth (mm) | How deep a layer of sand to lay, in millimetres. |
| Sand density (t/m³) | The density of the specific sand being used, in tonnes per cubic metre. Check the supplier’s figure where possible; 1.3 to 1.7 t/m³ is a commonly cited range depending on the sand type. |
| Bag size (kg) | The size of the bags being bought, in kilograms. |
| Price per tonne ($) | The price charged per tonne, for an estimated total cost. |
When to use it
Bedding sand under pavers or a slab
A bedding layer is usually specified as a shallow, fixed depth over the full area; entering that area and depth gives the volume, weight and bag count needed.
Filling a sandpit or sandbox
A sandpit’s footprint and the depth of play sand wanted give a straightforward volume and weight figure, along with the bag count if buying in smaller bags rather than bulk.
Comparing bagged versus bulk delivery
The bag count shows what buying in small bags would take, which can then be checked against a bulk tonne price to see which works out cheaper for the quantity needed.
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
How much sand is needed as depth increases
A fixed 4 m by 3 m area, laid at a range of depths.
| Depth | Sand needed | Bags needed |
|---|---|---|
| 25 mm | 0.450 tonnes | 23 × 20 kg bags |
| 50 mm | 0.900 tonnes | 45 × 20 kg bags |
| 75 mm | 1.350 tonnes | 68 × 20 kg bags |
| 100 mm | 1.800 tonnes | 90 × 20 kg bags |
| 150 mm | 2.700 tonnes | 135 × 20 kg bags |
| 200 mm | 3.600 tonnes | 180 × 20 kg bags |
How the weight needed changes with sand density
The same area and depth, across a density range typical of different sand types.
| Sand density | Sand needed | Bags needed |
|---|---|---|
| 1.3 t/m³ | 0.780 tonnes | 39 × 20 kg bags |
| 1.4 t/m³ | 0.840 tonnes | 42 × 20 kg bags |
| 1.5 t/m³ | 0.900 tonnes | 45 × 20 kg bags |
| 1.6 t/m³ | 0.960 tonnes | 48 × 20 kg bags |
| 1.7 t/m³ | 1.020 tonnes | 51 × 20 kg bags |
| 1.8 t/m³ | 1.080 tonnes | 54 × 20 kg bags |
Questions
How do I work out how much sand I need?
Multiply the area by the depth to get the volume, then multiply that volume by the sand’s density to get the weight. This calculator does that arithmetic and also converts the result into an estimated bag count and cost.
What density should I use for sand?
It depends on the type: dry loose sand is generally lighter, damp or compacted sand heavier, with published figures commonly falling somewhere between about 1.3 and 1.7 tonnes per cubic metre. Check the bag or delivery docket for the specific product where you can, since a single assumed figure will not be right for every sand.
Is this the same as the paver sand calculator?
It covers the same underlying maths but is meant for any general sand quantity, such as a sandpit, a general fill or levelling layer, rather than the specific bedding and joint-filling depths used under pavers. For paver work specifically, see the paver sand calculator.
Why does the bag count round up?
You cannot buy part of a bag, so the calculator rounds the required weight up to the next whole bag. That means the true amount bought will usually be slightly more than the calculated minimum.
For sand specifically as bedding or jointing under pavers, see the paver sand calculator. For a similar volume-and-weight calculation with gravel, see the gravel calculator.