Formula Used
Rectangle area = Length × Width Circle area = π × Radius² Triangle area = ½ × Base × Height Net volume = Area × Depth Adjusted volume = Net volume × (1 + Compaction %) × (1 + Waste %) Stone weight = Adjusted volume × Bulk density Bags required = Adjusted quantity ÷ Bag capacity Total cost = Materials + Delivery + Labour + Fixed costs + Tax
Convert every measurement into consistent base units. Apply depth after calculating each surface area. Round purchase quantities upward before ordering materials.
How to Use
- Add every separate garden, border, path, or feature area.
- Select each shape and enter its required measurements.
- Choose stone depth, type, density, and grading.
- Enter waste, compaction, bags, delivery, and supplier prices.
- Submit the form and review rounded purchase quantities.
- Export the result using copy, CSV, or PDF.
Measure finished surfaces rather than rough surrounding boundaries. Use supplier density data whenever it is available. Confirm access limits before arranging bulk stone delivery.
Stone Density Reference
| Stone type | Typical density | Common use |
|---|---|---|
| Pea gravel | 1,650 kg/m³ | Paths and borders |
| River rock | 1,700 kg/m³ | Drainage and features |
| Crushed stone | 1,600 kg/m³ | Paths and stable surfaces |
| Marble chips | 1,500 kg/m³ | Bright decorative coverage |
| Slate chips | 1,400 kg/m³ | Borders and modern gardens |
| Lava rock | 800 kg/m³ | Lightweight decorative beds |
| Granite chips | 1,680 kg/m³ | Durable paths and borders |
Densities vary with moisture, grading, and supplier processing. Loose stone may settle after placement and weathering. Use a measured supplier density for final purchasing.
Recommended Depth Guide
| Application | Typical depth | Planning note |
|---|---|---|
| Light decorative coverage | 25–35 mm | Best for small, even stone |
| Standard garden bed | 40–60 mm | Balances coverage and cost |
| Weed-control coverage | 50–75 mm | Use suitable landscape fabric |
| Pedestrian pathway | 60–100 mm | Prepare and compact the base |
| Driveway top layer | 75–125 mm | Confirm stone suitability first |
Large stones usually need deeper installation than fine gravel. Traffic areas also require stronger prepared sub-base layers. Always follow local and supplier installation guidance.
Worked Example
| Garden size | 6 m × 4 m |
|---|---|
| Stone depth | 50 mm |
| Net volume | 1.20 m³ |
| Allowances | 5% compaction and 10% waste |
| Adjusted volume | 1.386 m³ |
| Pea gravel weight | About 2,287 kg |
The example begins with twenty-four square metres. Its selected depth creates 1.20 cubic metres. Allowances increase the recommended quantity before ordering.
Buying and Measurement Tips
Measure curves using smaller rectangular or triangular sections. Keep delivery access clear for large vehicles. Check maximum load limits for driveways and paving.
Compare bag prices using equal weights or volumes. Include handling costs before choosing the cheapest quote. Order consistent batches to reduce visible colour differences.
Landscape fabric can limit stone mixing with soil. It does not replace proper drainage or preparation. Compact sub-base material before spreading decorative stone.
Frequently Asked Questions
How much extra stone should I order?
Many projects add five to ten percent waste. Compaction may require another separate allowance. Irregular layouts often benefit from a larger margin.
Should I calculate stone by weight or volume?
Suppliers commonly sell stone using either measurement. Density connects volume estimates with weight estimates. Use the supplier's selling basis for pricing.
Why does decorative stone density vary?
Stone type changes the solid material density. Moisture and grading change bulk density further. Supplier processing also affects packing and void spaces.
Can I calculate several garden areas together?
Yes, add every section using separate measurements. Each section can use another stone type. The calculator combines all quantities and project costs.
How deep should decorative gravel be?
Depth depends on stone size and intended traffic. Beds often need less depth than pathways. Always compare recommendations from your selected supplier.
Do I need landscape fabric?
Fabric may reduce mixing between soil and stone. It can also improve long-term maintenance. Drainage and soil conditions still need consideration.
How are bag quantities rounded?
The calculator always rounds required packages upward. Partial bags cannot normally be purchased. This approach helps prevent material shortages during installation.
Can I compare supplier prices?
Enter three prices using one shared selling basis. The calculator ranks their estimated material costs. Delivery differences should be entered separately when needed.
Does the result include sub-base material?
Enter a sub-base depth and density first. The calculator estimates its volume and weight. Its purchase cost remains inside additional fixed costs.
Are the estimates guaranteed?
No calculator can measure every site condition. Settlement and moisture can change final requirements. Confirm quantities with your stone supplier before ordering.
Important Disclaimer
This calculator provides planning estimates using entered measurements. Actual density, settlement, and delivery quantities may differ. Verify site conditions and supplier specifications before purchasing.