Typical bulk densities for gravel and aggregate
| Material | Typical bulk density |
|---|---|
| Pea gravel / rounded shingle | ~1.5 – 1.6 t/m³ |
| Crushed stone / angular aggregate | ~1.6 – 1.7 t/m³ |
| Compacted road-base aggregate | ~1.8 – 2.0 t/m³ |
- Bulk density is material- and moisture-dependent and can vary between suppliers of nominally the same product — always check the supplier's stated density for an accurate order quantity on larger jobs.
- This calculator does not account for compaction: gravel settles after placement and vehicular or foot traffic, so a top-up allowance is often needed for driveways over time.
What does a gravel calculator do?
A gravel calculator computes the volume of material needed to cover an area to a given depth, then converts that volume into a weight in tonnes using the bulk density of the specific gravel or aggregate product — the unit that most quarries and builders' merchants use for bulk delivery pricing. Bulk density varies by material type, particle size and moisture content; typical loose gravel and crushed stone aggregate fall in the range of about 1.5 to 1.7 tonnes per cubic meter.
For smaller garden or DIY jobs, the calculator also converts the total weight into a count of standard 25 kg bags, which is how gravel is commonly sold at retail rather than by bulk tonnage.
How to use this gravel calculator
- Enter the area to be covered in square meters.
- Enter the desired depth of gravel in centimeters — 5 cm (about 2 inches) is a common depth for a decorative or path top-up layer.
- Enter the bulk density of your specific gravel or aggregate in tonnes per cubic meter — check the supplier's product sheet, or use the 1.6 t/m³ default as a mid-range estimate.
- Read the volume in cubic meters, the estimated tonnes needed, and the equivalent number of 25 kg bags for retail purchase.
The formula behind gravel quantity
Volume equals area multiplied by depth (converted to meters). Weight in tonnes equals volume multiplied by the bulk density of the material. The bag count converts the total weight to kilograms and divides by 25, rounding up.
Worked example: a 20 m² area at 5 cm depth has a volume of 20 × 0.05 = 1 m³. At a bulk density of 1.6 t/m³, that is 1 × 1.6 = 1.6 tonnes, which equals 1.6 × 1000 ÷ 25 = 64 bags of 25 kg gravel.
Common mistakes
- Using a generic density figure instead of the specific value provided by the aggregate supplier.
- Entering depth in centimeters where meters were intended (or vice versa), which changes the volume result by a factor of 100.
- Not accounting for compaction and settling, which can reduce the effective depth over time on driveways and paths.
- Ordering by bag count for a large job, where bulk (loose or bulk-bag) delivery is typically far more cost-effective per tonne.
자주 묻는 질문
How much gravel do I need for a 20m² driveway?
At a 5 cm depth, a 20 m² area needs 20 × 0.05 = 1 cubic meter of gravel. At a typical bulk density of 1.6 t/m³, that is 1.6 tonnes, equivalent to about 64 bags of 25 kg gravel.
How many tonnes of gravel are in a cubic meter?
It depends on the bulk density of the specific material, but a common range for gravel and aggregate is about 1.5 to 1.7 tonnes per cubic meter. Always check the supplier's stated density for an accurate figure.
How deep should a gravel driveway be?
A common depth for a decorative or top-up gravel layer is around 5 cm (about 2 inches), though a structural driveway base layer is typically deeper — check local practice and your specific application.
Should I buy gravel in bags or bulk?
For small areas, bagged gravel (commonly sold in 25 kg bags) is convenient. For larger jobs, bulk delivery (loose tipped or in a bulk bag) is typically far more cost-effective per tonne than buying many individual bags.
참고 자료
- Typical bulk density ranges for gravel and crushed aggregate are drawn from standard construction materials references and quarry/builders' merchant product data sheets.
- Standard unit conversion: 1 tonne = 1,000 kilograms (SI mass unit definitions).