To determine how much gravel a driveway or path requires, multiply the surface area in square feet by the desired depth in feet, then divide by 27 to get cubic yards. A standard driveway depth is 4 to 6 inches of compacted gravel, while a walking path typically needs 2 to 3 inches. The volume formula does not change with gravel type, but the weight per cubic yard varies from 2,400 to 2,900 pounds depending on stone size and moisture.
Step 1: Measure the Area in Square Feet
For a rectangular driveway or path, measure length and width in feet and multiply them. For a circular path or a curved driveway, break the area into rectangles and triangles, calculate each separately, and add the results. A triangle area is half the base times the height. For irregular shapes, use a grid method: draw the outline on graph paper, count full squares inside, estimate partial squares, and convert each square to its real-world area.
If the driveway has a slope, measure the horizontal projected area rather than the sloped surface. A 10-foot-wide driveway that rises 1 foot over 20 feet of slope has a horizontal run of about 19.97 feet, not 20 feet. The difference is small for gentle slopes but becomes significant on steeper grades. Use a tape measure along the ground for length and a level for width, then apply the slope correction if the grade exceeds 10 percent.
For a path with straight edges but varying width, take width measurements at every 5 feet and average them. Multiply the average width by the total length. This method works well for paths that curve gently or widen at a gate. Record all measurements in feet, not inches or yards, to keep the volume formula consistent.
Step 2: Choose the Depth for the Application
Driveways that carry passenger cars need a compacted gravel depth of 4 inches minimum. A 6-inch depth is appropriate for heavier vehicles, frequent truck traffic, or soft soil conditions. Paths for foot traffic require only 2 inches of compacted gravel over a prepared base. A garden path with decorative stone can use 1.5 inches if the base is already firm.
The depth refers to the final compacted layer, not the loose volume delivered. When gravel is dumped and spread, it sits at a loose density. Compacting with a plate compactor or a roller reduces the layer thickness by 10 to 20 percent. To achieve a 4-inch compacted depth, order and spread about 4.5 to 5 inches of loose gravel. For a 6-inch compacted layer, start with 6.5 to 7.5 inches of loose material.
If the driveway has a sub-base of crushed stone, that layer is separate from the surface gravel. The sub-base typically uses 4 to 6 inches of larger crushed stone, while the top layer uses 2 to 3 inches of smaller gravel. Calculate each layer separately using the same area and depth formula, then add the volumes together.
Step 3: Convert Square Feet and Inches to Cubic Yards
Convert depth from inches to feet by dividing by 12. For a 4-inch depth, use 0.33 feet. For a 6-inch depth, use 0.5 feet. Multiply the area in square feet by the depth in feet to get cubic feet. Divide the result by 27 to get cubic yards, since one cubic yard equals 27 cubic feet.
For example, a 12-foot-wide by 40-foot-long driveway has an area of 480 square feet. At a 4-inch depth, the volume is 480 times 0.33, which equals 158.4 cubic feet. Dividing by 27 gives 5.87 cubic yards. Round up to 6 cubic yards for ordering. At a 6-inch depth, the same driveway needs 480 times 0.5, or 240 cubic feet, which equals 8.89 cubic yards, so order 9 cubic yards.
A path that is 3 feet wide and 60 feet long has an area of 180 square feet. At a 2-inch depth, the volume is 180 times 0.167, or 30.1 cubic feet. Dividing by 27 gives 1.11 cubic yards. Order 1.5 cubic yards to account for compaction loss and uneven spreading. Add 5 to 10 percent for waste and settling, and 15 percent if the ground is uneven or has deep ruts.
Step 4: Convert Cubic Yards to Tons for Ordering
Gravel is sold by the ton in many regions, so the volume must be converted to weight. The bulk density of mixed gravel ranges from 1.2 to 1.45 tons per cubic yard. A cubic yard of dry pea gravel weighs about 1.3 tons, while a cubic yard of wet crushed stone can weigh up to 1.5 tons. Use 1.4 tons per cubic yard as a general conversion factor when the specific material is unknown.
Multiply the cubic yards by the density factor. For the 6-cubic-yard driveway example, 6 times 1.4 equals 8.4 tons. Order 9 tons to cover compaction loss and delivery variance. For the 1.5-cubic-yard path, 1.5 times 1.4 equals 2.1 tons, so order 2.5 tons. If the gravel supplier lists material by the cubic yard, skip the tonnage conversion and order the volume directly.
Different gravel types have different densities. Angular crushed stone packs more tightly than round river rock, so a cubic yard of crushed stone weighs more than a cubic yard of pea gravel. Larger stones have more void space and weigh less per cubic yard than smaller stones of the same material. Check the supplier's specifications when available, and adjust the tonnage factor accordingly.
Step 5: Account for Compaction and Settling
Compaction reduces the volume of loose gravel. A plate compactor on a 4-inch layer can settle the material by 0.5 to 1 inch. This means an extra 12 to 25 percent of volume is needed to reach the final depth. For a path that is only hand-tamped, the settling is less, around 5 to 10 percent. Rain and vehicle traffic also cause settling over time, so a 10 percent contingency is prudent for most projects.
If the driveway has a border or edging, the gravel must fill flush with the edge. Add the volume for the edge area separately. For a driveway with a 4-inch-tall edge along both sides, multiply the length of each side by the edge height and the gravel depth, then add that volume to the main calculation. This is a small amount, usually less than 0.5 cubic yard, but it prevents a low spot at the border.
For a sloped driveway, the gravel may slide downhill during spreading. Use a slightly deeper layer at the top of the slope and a thinner layer at the bottom to compensate. Add an extra 5 percent for slopes over 10 percent grade. For paths on a hillside, use edging to hold the gravel in place and reduce the waste factor.
Step 6: Use a Final Checklist Before Ordering
Measure the length and width of the driveway or path in feet. Calculate the area in square feet. Select the compacted depth based on vehicle type or foot traffic. Convert the depth to feet and multiply by the area to get cubic feet. Divide by 27 to get cubic yards. Add 10 to 20 percent for compaction, settling, and waste. Convert to tons using 1.4 tons per cubic yard if the supplier prices by weight. Round up to the nearest half ton or whole cubic yard for ordering.
Verify the calculation by comparing the estimated volume to the supplier's delivery capacity. A standard dump truck carries 10 to 12 cubic yards, so a small driveway fits in one load. A path project may require only a fraction of a load, so check if the supplier has a minimum delivery fee. Confirm whether the gravel is sold by the cubic yard or by the ton, and use the matching unit in the final order.
Check the gravel type for the intended use. Pea gravel is comfortable for walking but shifts under vehicle tires. Crushed stone with angular edges locks together better for driveways. Decomposed granite is fine for paths but washes away on slopes. Select the material after the volume is calculated, since the density factor changes the tonnage but not the cubic yardage.