Landscape Rock / Decorative Stone Calculator
Enter the area dimensions, desired depth, and rock type to calculate how much decorative landscape stone you need in cubic yards, tons, and bags for your project.
Estimate only — not professional advice. Always verify results independently before purchasing materials or beginning work. Terms of Use
What is Landscape Rock / Decorative Stone?
A landscape rock calculator converts area dimensions and desired coverage depth into the volume and weight of decorative stone needed for landscaping projects. Unlike uniform materials such as sand or mulch, landscape rock varies enormously in density — lightweight lava rock weighs less than half as much as dense river rock per cubic yard — making weight calculations essential for ordering and delivery planning. The calculation follows three steps: compute the area in square feet, multiply by depth (converted to feet) to get cubic feet, then divide by 27 to convert to cubic yards. The weight calculation multiplies volume by the material's density in tons per cubic yard. Each rock type has a characteristic density based on its geological composition and size distribution. Pea gravel (3/8-inch smooth rounded stones) has a density of approximately 1.4 tons per cubic yard. It is popular for pathways, dog runs, and drainage applications. River rock (1-3 inch smooth rounded stones) weighs about 1.3 tons per cubic yard due to larger air voids between stones. Lava rock is dramatically lighter at 0.5 tons per cubic yard because of its porous volcanic structure — this makes it economical for large coverage areas where weight-based pricing applies. Large decorative boulders and dense crushed granite approach 1.5 tons per cubic yard. For small projects, landscape rock is available in bags typically containing 0.5 cubic feet each. This format is convenient for garden borders, small beds, and accent areas but becomes expensive at scale. For any project requiring more than 1-2 cubic yards, bulk delivery by the ton is far more economical — typically 50-75% cheaper per cubic foot than bagged product. Depth recommendations vary by application: use 2-3 inches for decorative ground cover over landscape fabric, 3-4 inches for pathways and high-traffic areas, and 4-6 inches for drainage applications. Larger rock sizes require greater depth because they do not pack as tightly — 3-inch river rock needs at least 3-4 inches of depth to achieve full coverage without fabric showing through.
How to Calculate
- Measure the length and width of the area to be covered in feet
- Determine the desired depth in inches (2-3 inches for decorative cover, 3-4 for paths)
- Select the rock type based on your design preference and application
- Review the volume in cubic yards and weight in tons for bulk ordering
- For small projects, check the bag count for purchasing at a garden center
- Contact a landscape supply yard with your tonnage for delivery pricing
Formula
Area = Length (ft) x Width (ft) Cubic Feet = Area x Depth (in) / 12 Volume = Cubic Feet / 27 Weight = Volume x Density (tons per cubic yard) Bags = ceiling(Cubic Feet / 0.5) Density values: Pea Gravel = 1.4 tons/yd, River Rock = 1.3 tons/yd, Lava Rock = 0.5 tons/yd, Large Boulders = 1.5 tons/yd. Bag size is the standard 0.5 cubic foot retail bag.
Example Calculation
A 15 ft x 10 ft area, 3 inches deep, with river rock (1.3 tons/cu yd): Area = 15 x 10 = 150 sq ft Cubic Feet = 150 x (3 / 12) = 150 x 0.25 = 37.5 cu ft Volume = 37.5 / 27 = 1.39 cu yd Weight = 1.39 x 1.3 = 1.81 tons Bags = ceiling(37.5 / 0.5) = 75 bags
Frequently Asked Questions
How deep should landscape rock be?
Decorative ground cover over landscape fabric needs 2-3 inches. Pathways and walkways need 3-4 inches for stability. Drainage applications (French drains, dry creek beds) need 4-6 inches. Larger rock sizes require proportionally greater depth — use a minimum depth of 1.5 times the average stone diameter for complete coverage.
Do I need landscape fabric under decorative rock?
Yes, for most applications. Landscape fabric (not plastic sheeting) prevents rock from sinking into soil and prevents weeds from growing up through the rock layer. Use commercial-grade woven fabric, not the thin spun-bond type. The only exception is dry creek beds and drainage areas where fabric would impede water flow — use no fabric or a high-flow drainage fabric instead.
How much does landscape rock delivery cost?
Bulk delivery typically costs $50-150 per load depending on distance from the quarry or supply yard. Most yards offer free delivery for orders over 5-10 tons. The rock itself ranges from $25-75 per ton for common types (pea gravel, crushed stone) to $100-300+ per ton for premium river rock, polished stone, or imported material.
Is it cheaper to buy bagged or bulk rock?
Bulk is dramatically cheaper for any quantity over half a cubic yard. Bagged pea gravel costs $4-6 per 0.5 cu ft bag ($216-324 per cubic yard). Bulk pea gravel costs $25-50 per ton delivered ($35-70 per cubic yard). You save 70-80% buying bulk. The break-even point is typically around 10-15 bags — beyond that, bulk delivery pays for itself even with the delivery fee.
What is the best rock for pathways?
Decomposed granite (DG) or 3/8-inch pea gravel provide the most comfortable walking surface and compact well for stability. Avoid large river rock (over 1 inch) for pathways — it shifts underfoot and is difficult to walk on. For wheelchair accessibility, use compacted decomposed granite or stabilized crushed stone with a binding agent.
How do I calculate rock for irregular shapes?
Break irregular areas into rectangles, triangles, and circles. Calculate each section separately and sum the volumes. For curved beds, use the average width at several points. For circular areas, use the formula: area = pi x radius squared. Most landscape areas can be approximated within 10% accuracy using simple geometric shapes.