Compacted vs loose gravel: which volume are you ordering?
Your patio drawing describes a finished base layer. A delivery truck brings loose aggregate. Both quantities may be correct, but they are not interchangeable.
By PatioBoQ · Updated · Methodology & limits
Start with the compacted layer
For a uniform layer, compacted volume is area multiplied by compacted thickness. A 20 × 14 ft patio covers 26.0128512 m². At an example compacted thickness of 150 mm, the base volume is 26.0128512 × 0.15 = 3.90192768 m³, or approximately 5.10 cubic yards.
That result describes the finished geometric layer. It is not a promise that ordering 5.10 loose cubic yards will produce that layer. The calculation also excludes any base extension beyond the paver edge; that area must be specified separately.
Three ways a supplier might quote
| Quote unit | Information you still need |
|---|---|
| Loose cubic yards | The supplier’s applicable loose-to-compacted relationship for the material and installation process. |
| US short tons | A suitable density or mass estimate and whether moisture changes the sale weight. |
| Bags or bulk bags | Whether each package is sold by mass or volume, its stated coverage, and rounding to whole packages. |
There is no universal conversion that this tool can safely apply to every gravel product. Material grading, voids and moisture affect the relationship. Ask the supplier what their quoted quantity means and ask the contractor which final compacted thickness is required.
Theoretical mass is still an assumption
If an illustrative compacted density is 2.0 tonnes/m³, the example base mass is 3.90192768 × 2.0 = 7.80385536 tonnes, approximately 8.60 US short tons. A tonne is 1,000 kg; a US short ton is 2,000 lb, or 907.18474 kg.
This is a mass estimate under a chosen density. It is not a live supplier order or a guaranteed delivered weight. If your supplier quotes a different density, use the one appropriate to the same physical state and material.
Do not multiply this mass by the soil swell factor. Soil swell is used for excavated spoil. It is not a general gravel purchasing allowance.
Avoid double counting
Suppose a supplier has already converted the required compacted volume into a delivery allowance. Adding another arbitrary “compaction percentage” may count the same allowance twice. Record the chain: required compacted layer → supplier’s conversion → final order units. Apply each factor once and state its source.
Keep paver cutting waste separate as well. A 10% paver allowance affects ordered surface material; it does not mean that every excavation and base quantity automatically increases by 10%.
Questions to ask before ordering
- Is the material specification suitable for the selected paving system?
- Does the quoted depth refer to loose placement or the finished compacted layer?
- Is the delivered quantity in loose cubic yards, short tons or metric tonnes?
- Has the allowance for base extension, material loss or delivery already been included?
- Who checks that the completed layer meets the project specification?
Use the paver base calculator for the geometric estimate, then document the supplier conversion separately.
Further reading
CMHA: Interlocking Concrete Pavers on an Aggregate Base provides a guide-specification framework. It does not make the example thickness or density on this page appropriate for every site.