Gravel Quantity Calculator
Written by Thierno Sadou Diallo, formula verified per our methodology • Last checked on 9/8/2026
Gravel volume is calculated with surface × thickness, and weight with volume × density. For 20 m² at 5 cm thick with gravel of density 1.6 t/m³, you need 1 m³ of gravel, or 1.6 tonnes.
Explanation
The amount of gravel needed depends on three factors: the surface to cover, the desired layer thickness (generally 3 to 5 cm for a pedestrian path or courtyard, more for a driveway that must support vehicle traffic), and the density of the gravel used, which varies significantly depending on the type of rock. Limestone gravel, lighter, has a density of about 1.4 to 1.5 tonnes per m³, while granite gravel, denser, often reaches 1.6 to 1.8 tonnes per m³ — a difference of 20 to 30% that directly affects the total weight to order and transport for the same volume. This calculator leaves the density adjustable rather than imposing a single value, the most reliable reference remaining the density indicated by the supplier for the specific gravel chosen.
Example: a 20 m² path at 5 cm thick
Inputs
Surface: 20 m². Thickness: 5 cm. Density: 1.6 t/m³.
Calculation
Volume = 20 × (5 ÷ 100) = 20 × 0.05 = 1 m³. Weight = 1 × 1.6 = 1.6 tonnes.
Result
You need 1 m³ of gravel, or 1.6 tonnes, for this path.
Frequently asked questions
What gravel thickness should be planned for a vehicle driveway?
A pedestrian path or courtyard generally only needs 3 to 5 cm of finishing gravel, laid on a stabilized foundation. A driveway intended for vehicle traffic requires a thicker structure (often a compacted base layer of 15 to 20 cm, topped with a finishing layer), to support the weight and avoid rutting.
How do I find the exact density of the gravel I plan to buy?
The supplier (quarry, building materials dealer) generally indicates the density or bulk weight of the gravel sold, which depends on the source rock and grain size. Absent precise information, a density of 1.5 to 1.6 t/m³ is a reasonable estimate for most common gravels.
Should an extra margin be planned, as with other materials?
A margin of 5 to 10% is generally sufficient for gravel, less critical than for cut materials (tile, roofing) since there is no loss from cutting. It mainly compensates for natural settling of the gravel after laying and small leveling adjustments.