Gravel Calculator
Calculate how many cubic meters and tons of gravel or crushed stone you need for a driveway, path or drainage, based on length, width and depth.
Density and bag size are editable example values, not specifications for your product. Allowance starts at 0%; ask the supplier about compaction.
Measure the space, then choose the product
- Measure the inside length and width in metres and the layer depth in centimetres. For an irregular area, calculate separate rectangles and add their volumes.
- Enter the supplier's loose bulk density and kilograms per bag. The defaults are examples; grading, packing and moisture change the weight.
- Set an explicit allowance if needed. The calculator shows the geometric volume separately from the quantity including your allowance, and rounds purchases up to whole bags.
What the numbers mean
Order volume = volume × (1 + allowance ÷ 100)
Weight in metric tonnes = order volume × bulk density in kg/m³ ÷ 1,000. One metric tonne (t) is 1,000 kg, not a US short ton. Bag count = weight in kg ÷ kg per bag, rounded up.
Example: a path with 20 kg bags
A 5 × 1.5 m path with a 5 cm layer has a volume of 0.375 m³. At the example density of 1,600 kg/m³ this is 600 kg: 30 bags of 20 kg, or one 800 kg bag. A chosen 10% allowance makes 0.4125 m³ and 660 kg, requiring 33 bags of 20 kg.
Allowance is not the same as volume loss
A 20% increase in your order and a 20% reduction during settling are different calculations. If a supplier specifies that the finished volume is 80% of the loose volume, divide the finished volume by 0.8: the required allowance is 25%. This is a mathematical example, not a recommendation for your material. Do not apply compaction twice if the supplier's conversion already includes it.
Frequently asked questions
What depth should I use?
Use the depth specified for your actual project. Ground conditions, load and material affect the design. Calculate each layer separately; this tool does not prescribe a safe driveway construction.
Why does changing density change the bag count?
Gravel bags here are measured in kilograms. A denser product needs more kilograms for the same volume, so it can require more bags.