Gravel Calculator

How to Calculate How Much Gravel You Need

Gravel is sold by weight (tons) for large orders and by volume (cubic yards) depending on your supplier. Getting the right amount requires calculating both volume — for coverage — and weight, since most gravel suppliers price and deliver by the ton.

The volume calculation is straightforward: length × width × depth (converted to feet). The weight calculation requires multiplying cubic yards by the gravel density, which varies by type. Crushed stone is denser than pea gravel; decomposed granite is denser still. This calculator handles the conversion automatically once you select your gravel type.

Gravel Types and Their Applications

Crushed Stone

Crushed stone (also called road base, crusher run, or #57 stone depending on grade) is the workhorse of the gravel world. Its angular, irregular shape causes particles to interlock and compact well, making it ideal for driveways, base layers, and any application requiring a stable, load-bearing surface. It does not shift under vehicle traffic the way rounded gravels do. Density: approximately 1.40 tons per cubic yard.

Pea Gravel

Pea gravel is rounded, smooth, and 3/8 to 1/2 inch in diameter. Its smooth surface makes it comfortable underfoot for paths and play areas. Because it does not interlock, it shifts under foot traffic and is not appropriate for driveways without a stable border and base. Pea gravel is popular for decorative landscaping, dog runs, and around playground equipment. Density: approximately 1.35 tons per cubic yard.

River Rock

River rock is larger (1–3 inches typically), naturally smooth, and highly decorative. It is used for drainage applications (dry creek beds, French drains), decorative borders, and low-maintenance ground cover. It does not compact, so it is not suitable for high-traffic areas. River rock is more expensive than crushed stone or pea gravel due to the washing and sorting required. Density: approximately 1.35 tons per cubic yard.

Decomposed Granite (DG)

Decomposed granite is granite that has naturally weathered into small particles ranging from fine powder to 1/4-inch pieces. When compacted, it creates a firm, permeable surface ideal for paths, patios, and driveways in dry climates. It is the most compaction-friendly of the decorative gravels. It is not appropriate for wet climates because it can wash away in heavy rain. Available in tan/gold, gray, and rust colors. Density: approximately 1.45 tons per cubic yard.

Gravel Depth Guide by Application

The right depth for gravel depends on its intended use and the amount of traffic it will receive:

• Decorative landscaping (2 inches): Minimal depth sufficient for decorative coverage. Adequate for areas with no foot traffic. Weeds will eventually push through — use landscape fabric underneath for weed control.
• Garden paths and light foot traffic (3 inches): Standard depth for most residential paths and stepping stone areas. Provides reasonable stability for walking.
• Standard residential driveway (4 inches): Adequate for regular passenger vehicle traffic on a well-prepared base. Most residential driveways use 4 inches of final surface material over a compacted base.
• Heavy vehicle driveway (6 inches): Required for trucks, RVs, and any driveway subject to heavy or frequent loads. For new driveways, lay a 4-inch compacted base layer of larger aggregate first, then top with 2–3 inches of finish gravel.
• Drainage applications: Depth depends on the specific drainage design. French drain trenches are typically filled to within 6 inches of the surface with washed stone.

Installing a Gravel Driveway

A well-built gravel driveway can last indefinitely with periodic maintenance. The key is proper installation from the start:

1. Excavate and grade: Remove all grass, vegetation, and topsoil to at least 6–8 inches below final grade. Grade for drainage — a 2% cross-slope sheds water to the sides.
2. Geotextile fabric: Install a non-woven geotextile fabric over the subgrade. This prevents subgrade soil from migrating up into the gravel base (pumping) while allowing water to drain through.
3. Base layer: Apply 4 inches of #21A or crusher run (angular crushed stone) and compact with a vibratory plate compactor. This base layer provides structural support.
4. Top layer: Apply 2–3 inches of finish gravel (#57 stone, pea gravel, or decomposed granite depending on aesthetic preference) and lightly compact.
5. Install edge restraints: Concrete curb, plastic landscape edging, or treated timber edge restraints prevent gravel from spreading onto lawns and adjacent areas.

Budget approximately 1 ton of gravel per 100 sq ft at 4-inch depth for the finish layer, plus 1.5 tons per 100 sq ft for the base layer. This gives a total of approximately 2.5 tons per 100 sq ft for a complete driveway installation.

Understanding Gravel Compaction

Gravel compacts when load is applied to it, reducing its volume. Angular crushed stone compacts more than rounded pea gravel because the irregular particles interlock and fill voids. When ordering gravel for driveways and compaction-required applications, add 10–15% to account for compaction loss.

For decorative applications where you do not want compaction (pea gravel paths, play areas), no compaction factor is needed. The calculator's 10–15% waste factor covers normal losses from spreading and incidental displacement.

When compacting crushed stone with a plate compactor, work in 3–4 inch lifts. Compacting more than 4 inches at a time is ineffective — the compaction force does not penetrate deeply enough. Make multiple passes in different directions for uniform compaction.

Gravel Driveway Maintenance

Even the best-built gravel driveway requires periodic attention:

• Annual regrading: Vehicle traffic displaces gravel toward the edges and creates low spots in the center. Regrade annually using a box grader or hand tools, redistributing gravel from edges back to the center.
• Top-dressing: Every 2–4 years, add a fresh 1–2 inch layer of surface gravel to replace material lost to compaction, displacement, and decomposition.
• Weed control: Weeds establish in gravel driveways despite their permeability. A pre-emergent herbicide applied in early spring dramatically reduces weed establishment. Spot-treat with herbicide as needed throughout the season.
• Drainage management: Keep drainage channels clear and ensure water does not pond on the driveway surface. Standing water causes rutting and accelerates gravel loss.
• Pothole repair: Fill potholes immediately with fresh crushed stone before they enlarge. Compact the patch firmly.

Common Gravel Calculation Mistakes

• Confusing tons and cubic yards: Gravel is heavy. 1 cubic yard of crushed stone weighs nearly 1.5 tons. Ordering 10 cubic yards when you need 10 tons (or vice versa) is a common and costly error.
• Not adding compaction factor: For driveways, the theoretical volume of gravel will compact by 10–15%. Always add this to your order.
• Wrong depth for application: Using 2-inch depth for a driveway that needs 4 inches means ordering half the material needed. Verify the recommended depth for your specific application.
• Skipping the base layer: Applying decorative gravel directly over unstable soil results in gravel sinking into the ground within one season. A fabric barrier and compacted base layer are essential for driveways and high-traffic areas.