Gravel Calculator

Whether you are building a driveway, laying a garden path, filling a drainage trench, or creating a decorative landscape bed, knowing how much gravel you need before ordering saves both money and time. Ordering too little means a second delivery fee and project delays. Ordering too much leaves you with excess material to store or dispose of. This calculator takes the guesswork out of the process by converting your project dimensions into precise volume and weight estimates, accounting for the specific density of the gravel type you plan to use.

Gravel is one of the most versatile materials in construction and landscaping. It serves as a base layer for pavers and concrete, a surface material for driveways and paths, a drainage medium around foundations and French drains, and a decorative element in xeriscaping and rock gardens. Each application may call for a different type and size of gravel, and the density varies accordingly. This calculator supports three common types — pea gravel, crushed stone, and river rock — each with its own density factor.

How the Calculation Works

The fundamental calculation is straightforward: multiply the length of the area by the width to get the surface area, then multiply by the depth to get the volume. In imperial units, length and width are entered in feet while depth is entered in inches (since gravel layers are typically measured in inches). The calculator converts inches to feet, computes the volume in cubic feet, and divides by 27 to convert to cubic yards — the standard unit for ordering bulk gravel in the United States.

In metric units, length and width are entered in meters and depth in centimeters. The calculator converts centimeters to meters and computes the volume in cubic meters. Weight is then calculated by multiplying the volume by the gravel density. The number of bags is determined by dividing the total weight by the standard bag size — 50 pounds for imperial or 25 kilograms for metric — and rounding up to the nearest whole bag.

Gravel Types and Their Densities

Pea gravel consists of small, naturally rounded stones typically 3/8 inch (10mm) in diameter. It has a slightly lower density than angular gravel because the rounded particles do not compact as tightly. This calculator uses approximately 1.35 tons per cubic yard (1,550 kg/m³) for pea gravel. It is commonly used for walkways, playgrounds, dog runs, and decorative garden features.

Crushed stone is mechanically broken rock with angular edges that interlock when compacted. It is the most common type for driveways, road base, and construction fill. The angular shape creates excellent compaction and load-bearing capacity. This calculator uses approximately 1.4 tons per cubic yard (1,600 kg/m³) for crushed stone.

River rock consists of naturally tumbled stones larger than pea gravel, typically 1–3 inches (25–75mm) in diameter. It is denser due to the larger stone size and is commonly used for drainage applications, dry creek beds, and decorative borders. This calculator uses approximately 1.45 tons per cubic yard (1,650 kg/m³) for river rock.

How Deep Should Your Gravel Be?

The appropriate depth depends on the application. For decorative garden paths and landscape beds, 2–3 inches (5–8 cm) is typically sufficient. Walkways that receive regular foot traffic perform well at 3–4 inches (8–10 cm). Driveways need a deeper layer — typically 4–6 inches (10–15 cm) of gravel over a compacted base layer. For drainage applications like French drains, depth depends on the specific engineering requirements of your project.

These depth figures are general references. Local soil conditions, expected traffic loads, and climate all influence the appropriate depth. Areas with freeze-thaw cycles may benefit from deeper gravel layers to prevent frost heave. If your project has structural requirements, consulting local building guidelines or a contractor for site-specific recommendations is advisable.

Ordering and Delivery

In the United States, bulk gravel is typically sold by the cubic yard or by the ton. One cubic yard of crushed stone weighs approximately 2,800 pounds (1.4 tons). Landscape supply companies and quarries often have minimum delivery quantities, commonly 1–2 cubic yards. For smaller projects, bagged gravel from a hardware store may be more practical, though the per-unit cost is higher.

When ordering, it is common to add 5–10% extra material to account for uneven terrain, settling, and spreading losses. This calculator provides the exact calculated quantity; consider adding a small buffer when placing your actual order. Delivery trucks can typically access driveways and larger staging areas, but you should confirm access requirements with your supplier if the delivery location has limited space.

Compaction and Settling

Freshly placed gravel settles over time, particularly angular crushed stone. Compaction reduces the volume by approximately 10–15%, meaning a 4-inch layer may settle to roughly 3.5 inches over time. If your application requires a specific finished depth, you may want to increase the initial depth accordingly. Mechanical compaction with a plate compactor accelerates this process and produces a more stable surface.

Pea gravel and river rock compact less than crushed stone because their rounded shapes do not interlock as effectively. For applications where stability matters — such as driveways or paver bases — crushed stone is generally preferred precisely because its angular particles lock together when compacted, creating a firm, stable layer.

Cost Considerations

Gravel prices vary significantly by region, type, and quantity. As a general reference in the US market, basic crushed stone costs approximately $30–65 per cubic yard for bulk delivery, while decorative pea gravel and river rock may range from $40–80 per cubic yard. Bagged gravel at retail typically costs $4–8 per 50-pound bag, which works out to a higher per-yard price but is convenient for small projects.

Delivery fees are often separate from material costs and depend on distance and quantity. Some suppliers offer free delivery above a minimum order, while others charge a flat fee. Getting quotes from multiple suppliers is recommended, as prices can vary substantially even within the same area.

Tips for Accurate Measurements

For rectangular areas, measuring length and width is straightforward. For irregular shapes, divide the area into approximate rectangles, calculate each section separately, and add the results together. You can run the calculator multiple times for different sections of a project and sum the totals.

If your area has a slope or uneven depth, measure the depth at several points and use the average. For example, if one end is 3 inches deep and the other is 5 inches deep, using an average depth of 4 inches will give a reasonable estimate. For areas with significant variation, erring on the side of ordering slightly more material helps avoid shortfalls.