Gravel Tonnage Calculator
Calculates the tonnage of gravel required to cover a given area at a specified depth. Ideal for driveways, pathways, and landscaping projects where you need to order aggregate by weight.
About this calculator
The weight of gravel needed is found by multiplying the volume of the space to be filled by the bulk density of the chosen gravel type: Tonnage = area × depth × density. Area is measured in m², depth in metres, and density in t/m³, giving a result in metric tonnes. Different gravel types have significantly different densities — pea gravel sits around 1.4 t/m³, while crushed limestone can reach 1.8 t/m³ — so selecting the correct gravel type is critical for an accurate order. Ordering by tonnage (rather than volume) matches how most suppliers price and deliver aggregate. Add 10–15% to your calculated tonnage to account for compaction and wastage during spreading.
How to use
Imagine you want to gravel a driveway: area = 50 m², desired depth = 0.05 m (5 cm), and you choose crushed granite with a density of 1.68 t/m³. Apply the formula: Tonnage = area × depth × density = 50 × 0.05 × 1.68 = 4.2 tonnes. Adding a 10% wastage buffer gives 4.2 × 1.1 = 4.62 tonnes to order. Enter your own coverage area, depth, and gravel type to get your required tonnage instantly.
Frequently asked questions
What is the density of common gravel types used in the calculator?
Density varies by gravel type: pea gravel is typically 1.4–1.5 t/m³, crushed limestone 1.6–1.7 t/m³, crushed granite 1.65–1.75 t/m³, and decomposed granite around 1.4 t/m³. River rock tends to be heavier at 1.7–1.8 t/m³. Using the wrong density can lead to ordering significantly too little or too much material, so always confirm the density with your supplier if it is not listed.
How deep should gravel be for a driveway versus a garden path?
For a driveway that carries vehicles, a minimum depth of 10 cm (100 mm) is recommended, ideally laid in two compacted layers of 5 cm each. A decorative garden path only needs 5–7 cm of gravel depth to look tidy and suppress weeds. High-traffic driveways may require a sub-base of larger stone beneath a finer top layer. Always account for settling — gravel compacts by roughly 20% after being driven over.
Why do I need to add extra tonnage for compaction and wastage?
Loose gravel compacts significantly once spread and trafficked, meaning the final depth will be less than the uncompacted volume suggests. A standard rule of thumb is to add 10–15% to your calculated tonnage to compensate. Wastage also occurs during delivery (spillage) and spreading around edges. For large projects, consult your supplier — they can advise on the exact compaction factor for the specific aggregate grade you are using.