Show the formula and working
This sand calculator works out how much sand you need for a patio bed, path, base, sandpit or any flat layer, in cubic metres, tonnes, small bags and bulk bags. It is built for UK and European projects measured in metres and millimetres, with a feet and inches switch, and it adds an allowance for compaction so you do not run short once the sand has been screeded and tamped.
Quick answer: Multiply length x width x depth in metres to get cubic metres, add about 10% for compaction and waste, then multiply by the density. A 4 m by 3 m area 50 mm deep needs 0.66 m³ of sharp sand, about 1.06 tonnes, which is 43 bags of 25 kg or 2 bulk bags. The sand calculator does this instantly.
What Is a Sand Calculator?
A sand calculator is a tool that turns the size and depth of an area into the volume and weight of sand needed, then into the number of bags to buy. For a rectangle, volume = length x width x depth, with the depth converted from millimetres to metres. For a circle, the area is 3.1416 x radius x radius, multiplied by the depth. The tool then adds your extra percentage for compaction and waste.
Weight is volume x loose bulk density. The indicative figures listed by Designing Buildings, the UK construction industry wiki, are about 1.54 tonnes per cubic metre for building sand and play sand and about 1.60 tonnes per cubic metre for concrete sand. Bags are the total weight divided by the bag weight, rounded up to whole bags. With the imperial switch on, the volume is also shown in cubic feet, using the exact definition on Wikipedia’s cubic foot page that one cubic metre is about 35.3147 ft³.
How Do You Use the Sand Calculator?
- Choose the Shape: a rectangle for most paths, beds and bases, or a circle for a round sandpit.
- For a rectangle enter Length and Width. For a circle enter Diameter.
- Enter the Depth of the finished sand layer in millimetres.
- Pick the Sand type. If your supplier gives a density, choose Custom density and type it into Custom density.
- Set Extra for compaction and waste. 10% suits most screeded or compacted layers.
- Enter the Small bag weight and Bulk bag weight shown by your merchant.
- Read the tonnes, cubic metres and bag counts, then open “Show the formula and working” to see each step with your numbers.
How Much Does 1 Cubic Metre of Sand Weigh?
One cubic metre of loose dry sand weighs roughly 1.5 to 1.6 tonnes, so a tonne of sand fills about 0.63 to 0.65 m³. Building sand (soft sand) is usually quoted at about 1,540 kg/m³ and sharp or concrete sand at about 1,600 kg/m³. Damp sand behaves differently: water clings to the grains and pushes them apart, so the same weight can take up more space until it is compacted.
Because density varies with the quarry, grading and moisture, the calculator lets you type your own figure. If a supplier sells by the tonne, use their stated density for the most accurate order.
How Many Bags of Sand Are in a Tonne?
A tonne of sand is 40 bags of 25 kg, or 50 bags of 20 kg. Small bags are handy for repairs and small jobs, but for anything over about half a tonne a bulk bag is usually easier to handle and leaves less plastic waste. Bulk bag weights vary between merchants, often somewhere around 750 to 900 kg, so the calculator uses 800 kg only as an example. Check the figure on the product listing before ordering.
How Much Extra Sand Should You Order?
Order about 10% more sand than the measured volume for any layer you will screed, tamp or compact. Loose sand settles as it is worked, some is lost on the ground and in the wheelbarrow, and real sites are rarely perfectly flat. Raise the extra to 15% or 20% if the ground is uneven or you are filling around obstacles, and lower it for a simple sandpit fill.
The same depth based method works for other layered materials. Our self levelling compound calculator uses length x width x depth for floor screeds, and you can browse more project tools on the home calculators hub.
Sand Needed per 10 m² by Depth
The table shows sand for every 10 m² of area before any extra for compaction and waste.
| Depth | Volume per 10 m² | Building sand (1,540 kg/m³) | Sharp sand (1,600 kg/m³) |
|---|---|---|---|
| 25 mm | 0.25 m³ | 0.39 tonnes | 0.40 tonnes |
| 50 mm | 0.50 m³ | 0.77 tonnes | 0.80 tonnes |
| 75 mm | 0.75 m³ | 1.16 tonnes | 1.20 tonnes |
| 100 mm | 1.00 m³ | 1.54 tonnes | 1.60 tonnes |
| 150 mm | 1.50 m³ | 2.31 tonnes | 2.40 tonnes |
Worked Example: Sand for a Patio Bed
Example: a rectangular area 4 m long and 3 m wide needs a 50 mm layer of sharp sand. The area is 4 x 3 = 12 m². The volume is 12 m² x 0.05 m = 0.6 m³, and with 10% extra for compaction and waste it becomes 0.66 m³. At 1,600 kg/m³ that weighs 1,056 kg, or about 1.06 tonnes. Divided into 25 kg bags you need 43 bags (42.24 rounded up), or 2 bulk bags of 800 kg. These are the default inputs, so the calculator shows the same figures when the page loads.
Sand Calculator FAQs
How do I calculate how much sand I need?
Multiply the length by the width by the depth, all in metres, to get cubic metres. Add about 10% for compaction and waste, then multiply by the density, around 1,600 kg/m³ for sharp sand, to get kilograms. Divide by the bag weight to get the number of bags.
How many square metres does a tonne of sand cover?
A tonne of sharp sand at 1,600 kg/m³ fills 0.625 m³, which covers about 12.5 m² at 50 mm deep, 25 m² at 25 mm deep or 6.25 m² at 100 mm deep. Take off around 10% for compaction and waste before relying on those figures.
What is the difference between sharp sand and building sand?
Sharp sand has coarser, angular grains that lock together, so it is used for paving beds, screeds and concrete. Building sand, also called soft sand, is finer and rounder, which makes smooth, workable mortar for bricklaying. Sharp sand is also slightly heavier per cubic metre.
Is a bulk bag of sand one tonne?
Not always. Many UK merchants sell bulk bags described as “jumbo” or “tonne” bags that actually hold somewhere around 750 to 900 kg, depending on the supplier and the material. Always check the stated weight on the listing and enter it in the calculator for an accurate bag count.
How do I convert cubic metres of sand to tonnes?
Multiply cubic metres by the density in tonnes per cubic metre. For sharp sand use about 1.6, so 2 m³ is about 3.2 tonnes. For building sand use about 1.54, so 2 m³ is about 3.08 tonnes. A supplier’s own density figure is more accurate than these averages.
How many bags of sand do I need for a sandpit?
Choose Circle or Rectangle, enter the size and the sand depth, and pick play sand. A round sandpit 2 m across filled 200 mm deep holds about 0.63 m³, which is roughly 0.97 tonnes of play sand at 1,540 kg/m³, or 39 bags of 25 kg before any extra.
Checked October 2026. Sources: Designing Buildings: Converting between weight and volume for bulk construction materials, Wikipedia: Cubic foot, merchant product listing for 800 kg washed building sand bulk bags (bag weight example).