Formula used
- Rectangle:
Area = Length × Width - Circle:
Area = π × Radius² - Triangle:
Area = Base × Height ÷ 2 - Trapezoid:
Area = (Base 1 + Base 2) × Height ÷ 2 - Required volume:
Net Area × Depth - Required weight:
Adjusted Volume × Adjusted Bulk Density - Adjusted quantity:
Base Quantity × (1 + Allowances ÷ 100) - Bags required:
Adjusted Weight ÷ Bag Weight - Total cost:
Material Cost + Delivery + Tax
How to use this calculator
- Add each landscaped area and select its shape.
- Enter the intended depth and pebble material.
- Choose realistic waste and settlement allowances.
- Select the supplier packaging method.
- Enter local prices, delivery, and tax values.
- Calculate, compare options, then export the results.
Example data
| Input | Example |
|---|---|
| Area | 5 m × 4 m rectangle |
| Depth | 50 mm |
| Material | River pebbles |
| Waste | 10% |
| Uneven ground | 5% |
| Settlement | 5% |
| Bag size | 20 kg |
| Bag price | £6.50 |
Frequently asked questions
How deep should decorative pebbles be?
Many projects use 40–75 mm. Larger pebbles often need greater depth.
Why does density affect the result?
Density converts required volume into weight. Suppliers may report different bulk densities.
Should I round bag quantities?
Whole bags should normally be rounded upward. This avoids material shortages.
What waste percentage should I use?
Ten percent is a common starting point. Complex edges may need more.
What does settlement allowance mean?
Pebbles can settle into the prepared base. Extra material maintains the intended depth.
Can I calculate several areas together?
Yes. Add separate rows for paths, borders, circles, and custom spaces.
What is supplier coverage mode?
It uses the bag label's stated coverage. Confirm the label depth matches your project.
Can I use imperial measurements?
Yes. Enter feet, inches, yards, square feet, or cubic yards.
How are pallets calculated?
The calculator divides bags by bags-per-pallet. Whole pallets are rounded upward.
Why can actual supplier totals differ?
Moisture, grading, density, packaging, and installation conditions can change coverage.
Is geotextile fabric always required?
Not always. It can reduce weed growth and separate pebbles from soil.
Important note
This calculator provides planning estimates. Supplier coverage and density can vary. Confirm quantities before purchasing materials.