How to Calculate Gravel and Fill
Find out how to calculate gravel and fill quantities in cubic yards or tons for driveways, trenches, and landscaping projects. Proper volume and weight calculations ensure you order the right amount.
Volume Formula for Rectangular Areas
The basic volume formula is Length × Width × Depth, where all measurements are in feet. Dividing the result by 27 converts cubic feet to cubic yards, which is how bulk materials like gravel are typically sold. For example, a 50 ft × 12 ft driveway with 4 inches (0.33 ft) of gravel requires 50 × 12 × 0.33 ÷ 27 ≈ 7.3 cubic yards.
Calculating Volume for Irregular Shapes
For curved or irregular areas, divide the shape into smaller rectangles or triangles, calculate each section's volume individually, and add them together. Alternatively, measure the average length and average width of the irregular area and multiply as if it were a rectangle — this approach is accurate enough for most landscape fill applications. A triangle's area is 0.5 × base × height, which you then multiply by depth.
Converting Cubic Yards to Tons
Gravel suppliers often price by the ton rather than the cubic yard. The conversion factor depends on material type: pea gravel weighs about 1.4 tons per cubic yard, while compacted crushed stone weighs about 1.5 tons per cubic yard, and sand about 1.35 tons per cubic yard. Multiply cubic yards by the material's weight factor to get the approximate tonnage to order.
Compaction Factor for Fill Material
When filling trenches or building up grade, loose fill compacts to a smaller volume after it is tamped or driven over. Most gravel and crushed stone compact by about 15–20 %, so you need to order more loose material than the finished volume requires. Divide your net volume by (1 − compaction rate): for a 10 cubic yard fill with 15 % compaction, order 10 ÷ 0.85 ≈ 11.8 cubic yards.
Gravel Depth Recommendations by Application
Residential driveways require 4–6 inches of compacted gravel base; heavy vehicle areas need 8–12 inches. Walkways and garden paths need a minimum 2–3-inch layer of decorative stone. Drainage trenches should be filled with clean angular stone (no fines) to a depth that meets local code, typically leaving 6 inches below the drain pipe elevation.
Ordering and Delivery Considerations
Most dump trucks carry 10–14 cubic yards per load, and some quarries have minimum order requirements of 3–5 cubic yards. Calculate whether multiple smaller deliveries or one larger load is more cost-effective given your site access and storage space. A full truck-load deposit can spread across the driveway and then be redistributed with a skid-steer rather than shoveling by hand.
Metric Volume Calculations
In metric units, calculate Length (m) × Width (m) × Depth (m) to get cubic meters directly. One cubic meter equals approximately 1.31 cubic yards and weighs roughly 1.5–2 tonnes depending on material. Suppliers in metric regions price by the cubic meter or tonne, so confirm your unit of sale before placing an order.
Try These Calculators
Put what you learned into practice with these free calculators.
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