Rock Calculator

1. Choose how you know the project area. Select rectangle for landscape beds, borders, and walkways. Use circle for tree rings or round garden beds. Pick triangle for corner areas. If you already measured the total square footage or cubic footage, select those options to skip dimension entry.
2. Enter your dimensions. Measure length and width in feet. For depth, most decorative rock beds use 2 to 3 inches. Walkways and drainage areas need 3 to 4 inches. Base rock under pavers or driveways may need 4 to 6 inches. The rock calculator converts inches to feet automatically. I've found that 2 inches looks full and raked-clean for rounded river rock, but 1 inch always shows bare ground between stones after a week of settling.
3. Select the rock type. Choose the closest match to what you're ordering. River rock, crushed rock, and decorative rock weigh about 1.4 to 1.5 tons per cubic yard. Lava rock is much lighter at 0.5 tons. Base rock and riprap run heavier at 1.6 to 2.0 tons. If your supplier quotes a specific density, use "Custom density." Mixing up base rock and decorative rock by accident is one of the most common ordering mistakes I see — base rock compacts hard and looks wrong in a flower bed.
4. Set the waste factor. 10% is a safe default for most landscape rock projects. Curved beds, tree rings, and areas around plants always use more than the math predicts. Drop to 5% only for flat rectangular beds with clean edges. Increase to 15% or 20% for irregular shapes or rocky subgrade.
5. Enter a price (optional). Choose whether your supplier sells by cubic yard or by ton, then enter the per-unit price. Landscape rock typically costs $25 to $70 per cubic yard or $35 to $80 per ton in most US markets (2026 prices). Delivery adds $50 to $150 per load depending on distance.
6. Review your results. The rock calculator shows cubic feet, cubic yards (before and after waste), estimated tons, and cost. Use cubic yards or tons when calling your supplier for a bulk delivery quote. Compare the before-waste and after-waste numbers to understand exactly how much extra you're ordering.

Pro tip: Measure the finished bed edge to edge after edging is installed so you don't over-order. On my last project, I measured before setting the border and ended up with nearly half a cubic yard of excess river rock in the driveway.

This rock calculator uses three steps: area, volume, and weight. Each step builds on the previous one so you can follow the math from your tape measure to an order quantity.

Volume:

Cubic feet = Area (sq ft) × Depth (ft)

Cubic yards = Cubic feet / 27

Weight:

Tons = Cubic yards × Density (tons per cubic yard)

With waste:

Order quantity = Base quantity × (1 + Waste % / 100)

Variables:

• Area = project surface in square feet (length × width for rectangles, π × radius² for circles, 0.5 × base × height for triangles)
• Depth = rock layer thickness in feet (divide inches by 12)
• Density = weight of one cubic yard of rock in tons (varies by rock type and moisture content)
• Waste factor = percentage added for uneven ground, edging, spreading loss, and curves

Density by rock type:

Example:

A landscape bed measures 20 × 5 feet at 2 inches deep, using river rock.

• Area = 20 × 5 = 100 sq ft
• Depth in feet = 2 / 12 = 0.167 ft
• Cubic feet = 100 × 0.167 = 16.7 ft³
• Cubic yards = 16.7 / 27 = 0.62 yd³
• Tons = 0.62 × 1.4 = 0.87 tons
• With 10% waste: 0.68 yd³ and 0.95 tons (order quantity)

At $45 per cubic yard, material cost for this bed would be about $30.60 before delivery. Many landscape beds look thin when rounded rock is spread below 2 inches, so avoid going shallower for decorative projects.

Why rock type changes the tonnage:

Cubic yards measure volume, not weight. Two cubic yards of lava rock (0.5 tons/yd³) weighs 1.0 ton, while the same two cubic yards of riprap (2.0 tons/yd³) weighs 4.0 tons. Always confirm whether your supplier sells by the cubic yard or by the ton before comparing prices.

Quick coverage reference: One cubic yard of rock at 2 inches deep covers about 162 sq ft. At 3 inches deep, one yard covers about 108 sq ft. At 1 inch deep, one yard stretches to 324 sq ft, but only lightweight lava rock looks acceptable that thin.

Assumptions:

• The project area has roughly uniform depth. For uneven ground, measure at several points and use the average
• Density values are dry-weight averages. Wet rock weighs 5% to 15% more, but suppliers typically sell by dry weight
• Driveway and base rock projects may need a compaction allowance (15% to 20% extra) beyond the standard waste factor
• Decorative rock needs a depth of at least 2× the rock diameter for full ground coverage
• The calculator does not include delivery, labor, or equipment rental costs