Enter your area dimensions and gravel depth to find out exactly how many tonnes, cubic metres, and bags of gravel or crushed stone you need. This gravel calculator supports rectangular and circular areas, eight material types, and an optional cost estimate — so you can order the right amount and avoid paying for excess material.
Ordering gravel without calculating the volume first is one of the most common and costly landscaping mistakes. Too little and you get bare patches and poor drainage. Too much and you pay disposal fees for material that goes to waste. This calculator uses exact geometry and tested material densities to give you a precise order quantity before you call your supplier.
How to Use This Calculator
- Choose metric or imperial. Switch between m/cm and ft/in using the unit toggle at the top. All inputs update their labels automatically.
- Select area shape. Use Rectangular for paths, driveways, and garden beds. Use Circular for round flower beds, fire pit rings, or ponds.
- Pick your material. Each material has a different density — gravel weighs more than mulch, decomposed granite more than pea gravel. Select the closest match from the dropdown.
- Enter dimensions and depth. Measure the length and width (or diameter), then enter the depth. For most decorative paths, 5 cm (2 in) is enough. Driveways need at least 10 cm (4 in).
- Enter price per tonne (optional). Add your supplier's rate to get a cost estimate alongside the volume and weight.
The Formula
All depth inputs in cm are converted to metres (÷ 100) before calculation. Inputs in inches are converted to metres (× 0.0254).
Example Calculation
A 5 m × 3 m garden path at 5 cm depth, filled with standard gravel (density 1,520 kg/m³):
- Area: 5 × 3 = 15 m²
- Depth: 5 cm = 0.05 m
- Volume: 15 × 0.05 = 0.75 m³
- Weight: 0.75 × 1,520 = 1,140 kg = 1.14 tonnes
- Bags (25 kg): ⌈1,140 ÷ 25⌉ = 46 bags
- Cost at £45/tonne: 1.14 × 45 = £51.30
Reference: Material Densities & Recommended Depths
| Material | Density (kg/m³) | Min Depth | Best Used For |
|---|---|---|---|
| Gravel (standard) | 1,520 | 5 cm / 2 in | Paths, driveways, drainage |
| Crushed Stone | 1,600 | 10 cm / 4 in | Driveways, sub-base, heavy traffic areas |
| Pea Gravel | 1,400 | 5 cm / 2 in | Decorative paths, play areas, borders |
| Decomposed Granite | 1,922 | 5 cm / 2 in | Xeriscape, desert gardens, stable paths |
| Sand | 1,600 | 2.5 cm / 1 in | Paver bedding, sandboxes, levelling |
| Topsoil | 900 | 10 cm / 4 in | Garden beds, lawn topdressing |
| Wood Mulch | 400 | 7 cm / 3 in | Tree rings, garden beds, weed suppression |
| Limestone Chips | 1,540 | 5 cm / 2 in | Decorative garden areas, pathways |
Common Mistakes to Avoid
Using too shallow a depth
A 2 cm layer of gravel looks thin after settling and allows weeds to push through. For paths, 5 cm is the practical minimum. For driveways that carry vehicles, use at least 10 cm.
Ignoring compaction
Loose gravel compacts by 20–30% after settling and foot or vehicle traffic. For driveways, order 15–20% more than the calculated volume to account for this.
Using the wrong material type
Pea gravel rolls underfoot and is unstable on slopes. Decomposed granite compacts to a firm surface. Crushed stone locks together best for driveways. Choose by function, not just appearance.
Measuring without edging
Without border edging or landscape fabric, gravel migrates into lawns over time. Always install edging before spreading, and factor in that the first year usually needs a light top-up.
When This Calculator Is Useful
🚗 Driveway Resurfacing
Calculate crushed stone needed for a full-depth driveway installation or top-up layer, then get the weight in tonnes to call your supplier with a precise order.
🌿 Garden Path Landscaping
Size up pea gravel or limestone chips for a decorative garden path, including optional cost estimate before visiting the garden centre.
🏗️ Contractor Quoting
Landscapers and builders use the weight and volume outputs to build accurate material cost quotes before bidding on a project.
💧 Drainage & Sub-Base
Calculate the gravel volume needed for a French drain, soakaway, or foundation sub-base layer before ordering from a bulk aggregate supplier.
Results are estimates based on standard material densities and ideal conditions. Actual quantities may vary due to material grade, compaction rate, site irregularities, and spillage. Always verify your order with a qualified contractor or aggregate supplier before purchasing. The construction disclaimer applies: add 10–15% to your calculated volume as a standard waste buffer.