What this calculator does
This tool determines both the volume and weight of gravel needed to cover a rectangular area to a specified depth. You enter the length and width of your project space in feet, plus the desired depth in inches, and it calculates cubic yards of material and approximate weight in tons. This helps you order the right amount and understand delivery and spreading costs.
The formula
Volume (cubic yards) = (Length × Width × Depth ÷ 12) ÷ 27
Then: Weight (tons) = Volume × 1.5 (standard gravel density)
Worked example
Let's say you're building a gravel driveway that's 20 feet long, 10 feet wide, and you want it 4 inches deep.
Step 1: Convert depth to feet
- 4 inches ÷ 12 = 0.33 feet
Step 2: Calculate cubic feet
- 20 ft × 10 ft × 0.33 ft = 66 cubic feet
Step 3: Convert to cubic yards
- 66 cubic feet ÷ 27 = 2.44 cubic yards
Step 4: Estimate weight
- 2.44 cubic yards × 1.5 tons per cubic yard = 3.67 tons
Result: You'd need approximately 2.5 cubic yards, or about 3.7 tons of gravel.
If your supplier charges $45 per ton, that's roughly $166 for material. Adding 15% for settling and compaction brings you to 2.8 cubic yards—a practical buffer for a driveway that will see foot and vehicle traffic.
Common mistakes to avoid
Forgetting to add extra for settling: Gravel compacts significantly in the first few months, especially under traffic. A 4-inch layer will settle to closer to 3.5 inches. Always order 10–15% more than the calculator shows, particularly for driveways and high-traffic areas.
Mixing up depth units: The calculator takes depth in inches, not feet. A common error is entering "1" thinking it means 1 inch when you actually need 12 inches (1 foot). Double-check your depth value before calculating.
Using the wrong density: Standard pea gravel and crushed limestone both weigh about 1.5 tons per cubic yard, which this calculator assumes. Marble chips, river rock, and decorative gravels can be heavier—check with your supplier. Conversely, lightweight lava rock weighs less, so you'd need more volume to reach the same weight.
Underestimating irregular shapes: If your driveway has curves, a turnaround, or tapers, break it into smaller rectangles. Calculate each section separately and add them together for accuracy. Eyeballing an irregular area almost always results in ordering too little.
Not accounting for drainage slope: Driveways should slope slightly for water runoff. If you're sloping the surface, the depth varies—use an average depth for the calculation, or treat the high and low ends as separate sections.