Calculate how much gravel you need for a driveway, walkway, patio, drainage layer, landscaping project or other surface. Enter the area dimensions, gravel depth and waste allowance to estimate the required volume and weight.
How the Gravel Calculator Works
Gravel quantity starts with the surface area and the required depth. Multiply the length by the width to find the area, then multiply the area by the gravel depth to find the base volume.
Surface Area = Length × Width
Gravel Volume = Surface Area × Depth
Planning Volume = Gravel Volume × (1 + Waste ÷ 100)
Estimated Weight = Planning Volume × Bulk Density
The calculator converts the entered measurements to metres internally. The final volume is shown in cubic metres, cubic feet and cubic yards so you can compare the result with supplier quantities.
Worked Gravel Example
Suppose a driveway is 10 metres long and 5 metres wide. The planned gravel depth is 100 mm, with a 10% waste allowance.
Area = 10 × 5 = 50 m²
Depth = 100 mm = 0.10 m
Base Volume = 50 × 0.10 = 5 m³
Planning Volume = 5 × 1.10 = 5.5 m³
The project therefore needs approximately 5.5 m³ of gravel after the 10% allowance. If the bulk density is 1,600 kg/m³, the estimated weight is about 8.8 tonnes.
Common Gravel Depths
The correct depth depends on the project, base preparation, aggregate size and how the finished surface will be used. These figures are starting points rather than structural specifications.
| Project | Typical Starting Depth | Approx. Metric Depth |
|---|---|---|
| Light landscaping | 1.5 to 2 in | 40 to 50 mm |
| Garden paths | 2 to 3 in | 50 to 75 mm |
| Driveway surface | 3 to 4 in | 75 to 100 mm |
| Decorative ground cover | 1.5 to 3 in | 40 to 75 mm |
Driveways and other load-bearing surfaces often require a properly prepared sub-base and more than one aggregate layer. Final specifications should follow local construction practice and the aggregate supplier's recommendations.
Gravel Volume Conversions
| Volume | Equivalent |
|---|---|
| 1 m³ | 35.315 ft³ |
| 1 m³ | 1.308 yd³ |
| 1 yd³ | 0.765 m³ |
| 1 ft³ | 0.0283 m³ |
How Much Gravel Do You Need?
The amount of gravel depends mainly on the surface dimensions and finished depth. For example, a 20 m² area at 50 mm depth requires 1 m³ before waste. At 100 mm depth, the same area requires 2 m³.
| Area | Depth | Base Volume | With 10% Waste |
|---|---|---|---|
| 10 m² | 50 mm | 0.50 m³ | 0.55 m³ |
| 20 m² | 50 mm | 1.00 m³ | 1.10 m³ |
| 20 m² | 100 mm | 2.00 m³ | 2.20 m³ |
| 50 m² | 100 mm | 5.00 m³ | 5.50 m³ |
| 100 m² | 75 mm | 7.50 m³ | 8.25 m³ |
Choosing a Bulk Density
Gravel does not have one fixed weight per cubic metre. Crushed stone, pea gravel, limestone, granite and other aggregates have different densities. Moisture and compaction also affect the final weight.
If a supplier gives you a bulk density, enter that figure into the calculator. If you do not have one, the default 1,600 kg/m³ provides a general planning estimate, not a purchase specification.
Common Gravel Calculation Mistakes
- Using the wrong depth: Measure the planned finished depth in several locations, especially where the existing ground is uneven.
- Forgetting waste: Some gravel is lost during delivery, spreading and compaction.
- Confusing tonnes with cubic metres: Volume and weight are different measurements. Density is needed to convert between them.
- Ignoring the sub-base: A gravel driveway often needs a suitable base layer below the visible aggregate.
- Using the wrong supplier density: A generic density is useful for planning, but supplier data gives a more useful weight estimate.
- Buying by volume without checking the supplier's unit: Suppliers sell aggregate by cubic metre, tonne, bag, bulk bag or other units depending on the market.
Gravel Calculator FAQs
How do I calculate how much gravel I need?
Multiply the length by the width to find the surface area. Multiply the area by the required depth in metres to get cubic metres. Add a waste allowance for the amount you plan to order.
How many tonnes of gravel do I need?
Multiply the required volume in cubic metres by the gravel's bulk density in kilograms per cubic metre, then divide by 1,000 to convert kilograms to tonnes. Density varies by aggregate type, so supplier data gives the most useful estimate.
How much gravel do I need for a driveway?
Calculate the driveway's surface area and multiply it by the planned gravel depth. A visible gravel layer often falls around 75 to 100 mm, but the required construction depth depends on the site, traffic, sub-base and aggregate type.
How much waste should I add to a gravel calculation?
A 5% to 10% allowance is useful for many straightforward areas. Uneven ground, irregular shapes, difficult access and spreading losses can justify a higher allowance.
How many cubic yards are in one cubic metre of gravel?
One cubic metre is approximately 1.308 cubic yards. The calculator converts cubic metres to cubic yards automatically.
Does gravel depth affect the quantity?
Yes. Doubling the depth doubles the required volume when the surface area stays the same. Always enter the intended finished depth rather than the aggregate thickness from an unrelated project.