How much gravel should you buy?
Start with the volume to cover, then convert it to weight using the chosen material’s density. Packaging turns that requirement into tonnes delivered or whole bags to buy.
Example: 20 m² of gravel at 5 cm
A 5 × 4 m area at 5 cm needs 20 × 0.05 = 1 m³ before allowance. At an assumed 1,600 kg/m³, that is 1,600 kg. In uncompacted mode, an example 10% allowance gives 1.10 m³ or 1,760 kg.
These are example inputs. Suitable depth depends on use and stone size. Calculate a foundation and a decorative finish separately using their own materials.
Weight (kg) = area (m²) × depth (cm) ÷ 100 × density (kg/m³)
Stone size is not weight per cubic metre
A grading such as 8/12 mm describes grain size, not the weight of 1 m³. Rock type, gaps between grains and moisture affect the delivered bulk density.
The tool’s values are editable starting points, not a product certificate. Ask your supplier for the weight per cubic metre of the material supplied. Divide kilograms by 1,000 to get tonnes: 1,760 kg = 1.76 t.
When the requested depth is after compaction
Compacted mode converts the final volume to a loose delivery volume. For an example final 1 m³, a factor of 1.15 and a 10% allowance give 1 × 1.15 × 1.10 = 1.265 m³. At a delivered density of 1,600 kg/m³, this is 2,024 kg.
Confirm the factor for the actual material and compaction method. Do not combine compacted density with a factor intended for loose supply. Uncompacted mode does not apply this factor.
Delivery volume with allowance = final volume × supply factor × (1 + allowance ÷ 100)
Compare whole bags, bulk bags and loose delivery
Bag counts round upwards. For the uncompacted example’s 1,760 kg, these selected pack sizes produce different purchases. Check the weight advertised by your own seller.
Bag prices use whole packs purchased; loose supply uses required tonnes multiplied by price per tonne. Add delivery, minimum orders and unloading before comparing.
| Packaging | To buy | Purchased weight |
|---|---|---|
| 25 kg bag | 71 bags | 1,775 kg |
| 1,000 kg bulk bag | 2 bulk bags | 2,000 kg |
| Loose | 1.76 tonnes | 1,760 kg before supplier rounding |
Example budget and next steps
At fictional prices of €149 per 1,000 kg bulk bag or €85 per loose tonne, 1,760 kg costs €298 in two bulk bags or €149.60 loose before fees. These are not market prices: enter your quotes.
Continue to geotextile, excavation or paving with the same project zone. Excavation depth and gravel depth are different inputs. Save your choices in My projects for the next visit.
Common mistakes
- Assuming 1 m³ always weighs one tonne.
- Treating a bulk bag as a fixed volume without checking its weight.
- Adding the same allowance twice.
- Confusing final compacted depth with loose delivery depth.
Before ordering
How many square metres does one tonne cover?
Divide 1,000 kg by density, then by depth in metres. With an assumed 1,600 kg/m³ at 5 cm, one tonne covers 12.5 m² before allowance and without a compaction factor.
Does a bulk bag always contain 1 m³?
No. Check the amount sold. A 1,000 kg bag holds 0.625 m³ at 1,600 kg/m³; another material gives another volume.
Is the suggested depth enough for vehicles?
The tool estimates quantity, not load-bearing performance. Confirm the foundation, materials and depths suited to vehicle use and your ground.
Is my terrace shape kept?
Yes, through a saved zone or project continuation links. At a given depth, weight uses the real plan area rather than an approximate rectangle.
Confirm quantities with your supplier
Cemex distinguishes volume and tonnage for the selected aggregate. Our example densities, prices and factors are not guaranteed product values. Cemex — Aggregates