Paver Sand Calculator
Sand is measured by volume and sold by weight, and density is what bridges the two, so it is an input: about 1,500 kg/m³ dry and 1,900 kg/m³ wet. A 20 m² patio bedded 3 cm deep is 0.6 m³; with 10% waste that is 0.66 m³, which at 1,500 kg/m³ weighs 990 kg — 39.6 bags of 25 kg, so 40 bags. One tonne bulk bag holds about the same, and at this size bulk works out cheaper.
Your numbers
Sand needed
990kg
Bags needed
40bags
Volume
0.66m³
Formula
Sand needed = Area × Layer depth ÷ 100 × (1 + Waste allowance ÷ 100) × Sand density, Bags needed = ⌈Sand needed ÷ Bag weight (kg)⌉
Sand loses 10–15% of its depth once compacted, so enter the finished depth rather than what you measure while spreading. Joint sand swept in afterwards is separate and adds another 1–2 kg per square metre.
What to enter
| Input | Default | Accepted range |
|---|---|---|
| Area (m²)The space a shape covers — length squared. | 20 | 0 and up |
| Layer depth (cm)How thick the layer will be laid. | 3 | 0 and up |
| Sand density (kg/m³)The weight of a cubic metre of sand: about 1,500 kg/m³ dry, 1,900 kg/m³ wet. | 1,500 | 0 and up |
| Bag weight (kg)The weight of one bag; 20, 25 and 40 kg are common and printed on the front. | 25 | 0 and up |
| Waste allowance (%)The extra bought to cover breakage and offcuts. | 10 | 0 ~ 50 |
Step by step
Quick reference table
Results when only Area (m²) changes and everything else stays put.
| Area (m²) | Sand needed (kg) | Bags needed (bags) | Volume (m³) |
|---|---|---|---|
| 10 | 495 | 20 | 0.33 |
| 15 | 743 | 30 | 0.495 |
| 20 | 990 | 40 | 0.66 |
| 30 | 1,485 | 60 | 0.99 |
| 40 | 1,980 | 80 | 1.32 |
What each result means
| Result | At default values |
|---|---|
| Sand needed (kg)The weight of sand to order, waste included — sand is sold by weight. | 990 |
| Bags needed (bags)How many bags to buy; they are not sold in fractions, so this rounds up. | 40 |
| Volume (m³)The space a solid holds — length cubed. | 0.66 |
Common mistakes
Sand loses 10–15% of its depth once compacted, so enter the finished depth rather than what you measure while spreading. Joint sand swept in afterwards is separate and adds another 1–2 kg per square metre.
Glossary
- Area
- The space a shape covers — length squared.
- Layer depth
- How thick the layer will be laid.
- Sand density
- The weight of a cubic metre of sand: about 1,500 kg/m³ dry, 1,900 kg/m³ wet.
- Bag weight (kg)
- The weight of one bag; 20, 25 and 40 kg are common and printed on the front.
- Waste allowance
- The extra bought to cover breakage and offcuts.
- Sand needed
- The weight of sand to order, waste included — sand is sold by weight.
- Bags needed
- How many bags to buy; they are not sold in fractions, so this rounds up.
- Volume
- The space a solid holds — length cubed.
Frequently asked questions
Q. How is Paver Sand Calculator calculated?
Sand needed = Area × Layer depth ÷ 100 × (1 + Waste allowance ÷ 100) × Sand density, Bags needed = ⌈Sand needed ÷ Bag weight (kg)⌉ — Sand is measured by volume and sold by weight, and density is what bridges the two, so it is an input: about 1,500 kg/m³ dry and 1,900 kg/m³ wet. A 20 m² patio bedded 3 cm deep is 0.6 m³; with 10% waste that is 0.66 m³, which at 1,500 kg/m³ weighs 990 kg — 39.6 bags of 25 kg, so 40 bags. One tonne bulk bag holds about the same, and at this size bulk works out cheaper.
Q. Can you walk through an example?
With Area 20m², Layer depth 3cm, Sand density 1,500kg/m³, Bag weight (kg) 25, Waste allowance 10%, the answer is Sand needed 990kg.
Q. What do I need to enter?
Enter Area, Layer depth, Sand density, Bag weight (kg), Waste allowance. The result recalculates as you type, and an empty box counts as zero.
Q. How much does the answer move if I change a number?
Changing only Area (m²) moves the answer to Area (m²) 10 → Sand needed (kg) 495 and Area (m²) 40 → Sand needed (kg) 1,980. The table below lays out five steps.
Q. How are the numbers rounded?
Money is shown to the nearest whole unit, percentages to one decimal place and everything else to two. What you see is rounded; the calculation itself carries the unrounded value forward.
Q. Anything to watch out for?
Sand loses 10–15% of its depth once compacted, so enter the finished depth rather than what you measure while spreading. Joint sand swept in afterwards is separate and adds another 1–2 kg per square metre.
Related calculators
Keep your length units consistent across inputs — mixing centimetres and metres throws results far off.