Last updated: July 6, 2026
Landscape Rock Calculator
Landscape rock sells by the ton, but your project is measured in square feet and depth. This calculator bridges that gap — converting your coverage area into cubic yards, tons, bags, and total cost across 9 common materials.
Quick Reference
Rock Type Comparison
Different rocks have different densities, which directly affects how many tons you need. Here's how common landscape rocks compare:
| Rock Type | Density (lb/ft³) | Tons/Yard³ | Best For |
|---|---|---|---|
| Pea Gravel | 100 | 1.35 | Walkways, patios, gardens, drainage |
| Crushed Stone | 110 | 1.49 | Driveways, road base, French drains |
| River Rock | 105 | 1.42 | Dry creek beds, decorative borders |
| Decomposed Granite | 95 | 1.28 | Walkways, rustic patios, xeriscaping |
| Lava Rock | 55 | 0.74 | Garden beds, planters, fire pits |
| Limestone | 100 | 1.35 | Driveways, agricultural use |
| Marble Chips | 110 | 1.49 | Decorative borders, garden accents |
| Flagstone | 150 | 2.03 | Patios, stepping stones, walkways |
| Riprap | 110 | 1.49 | Erosion control, shorelines, drains |
How Deep Should I Go?
Depth depends on your project. Too thin and rock shifts or exposes soil. Too deep and you waste money.
| Depth | Best For | Sq Ft per Ton (Pea Gravel) |
|---|---|---|
| 2 inches | Decorative ground cover, mulch replacement | 120 ft² |
| 3 inches | Walkways, garden paths | 80 ft² |
| 4 inches | Driveways, high-traffic areas | 60 ft² |
| 6 inches | Drainage projects, dry creek beds | 40 ft² |
How to Use This Calculator
Step 1: Choose your area shape — Rectangle for standard beds, Circle for tree rings, or Total Area if you already know the square footage.
Step 2: Enter dimensions. For rectangle, enter length and width. For circle, enter diameter. For total area, enter square footage directly.
Step 3: Set depth using the preset buttons (2"–6") or enter a custom value.
Step 4: Select rock type and enter price per ton. The calculator auto-updates the default price when you change rock type.
Step 5: Add optional costs — delivery fee, landscape fabric per square foot, and bag size for retail purchases.
Step 6: Results show instantly — tons, cubic yards, bag count, cost breakdown, and total with all extras.
Rock Calculator Formula
The calculator converts area and depth into rock quantity and cost:
- Rectangle: Area = Length × Width
- Circle: Area = π × (Diameter ÷ 2)²
- Volume (ft³) = Area (ft²) × (Depth in inches ÷ 12)
- Volume (yd³) = Volume (ft³) ÷ 27
- Tons = Volume (ft³) × Density (varies by rock type) ÷ 2,000
- Tons with Waste = Tons × (1 + Waste Factor ÷ 100)
- Rock Cost = Tons with Waste × Price per Ton
- Total Cost = Rock Cost + Fabric Cost + Delivery Fee
Density varies significantly by rock type. Lava rock weighs about 0.74 tons per cubic yard, while flagstone can weigh over 2 tons per cubic yard. The rock type dropdown adjusts the density automatically.
Worked Example: 200 sq ft Pathway with Pea Gravel
Let's calculate rock for a 20 ft × 10 ft pathway at 3 inches deep using pea gravel (100 lb/ft³) with 10% waste.
Step 1: Calculate volume:
Cubic Yards = 50 ÷ 27 = 1.85 yd³
Step 2: Calculate tons:
With 10% waste = 2.5 × 1.10 = 2.75 tons
Step 3: Calculate cost at $50/ton:
Cost per ft² = $137.50 ÷ 200 = $0.69/ft²
Total: 2.75 tons of pea gravel at $137.50. Use the calculator above to model your own project.
Tips & Common Mistakes
✓ Best Practices
- Lay landscape fabric first – prevents weeds and keeps rock from sinking into soil.
- Use edging or borders – contains rock and prevents migration into lawn or beds.
- Order 10% extra – rock settles and shifts; extra covers uneven spots.
- Consider drainage – rock is permeable; use it strategically to direct water flow.
- Match rock to setting – river rock for dry creek beds, crushed granite for pathways.
✗ Avoid This
- Skipping landscape fabric: Weeds grow through rock without a barrier underneath.
- Too thin an application: Under 2 inches lets soil show through and weeds penetrate.
- Mixing rock sizes: Different sizes look messy and don't interlock properly.
- Ignoring drainage: Rock dams can redirect water toward your foundation.
- Not measuring the area: Guessing leads to expensive over-ordering or frustrating under-ordering.
Material Weight & Coverage per Ton
Different rock types have vastly different densities. One ton of pea gravel covers more area than one ton of river rock — and understanding this prevents under-ordering.
| Material | Weight per Cu Ft | Cu Ft per Ton | Coverage at 2 in Deep | Coverage at 4 in Deep |
|---|---|---|---|---|
| Pea Gravel | 95 – 105 lbs | 19 – 21 | 114 – 126 sq ft | 57 – 63 sq ft |
| Crushed Stone (¾ in) | 100 – 115 lbs | 17 – 20 | 102 – 120 sq ft | 51 – 60 sq ft |
| River Rock (1–3 in) | 100 – 120 lbs | 17 – 20 | 102 – 120 sq ft | 51 – 60 sq ft |
| Decomposed Granite | 105 – 120 lbs | 17 – 19 | 102 – 114 sq ft | 51 – 57 sq ft |
| Marble Chips | 110 – 120 lbs | 17 – 18 | 102 – 108 sq ft | 51 – 54 sq ft |
| Lava Rock | 40 – 55 lbs | 36 – 50 | 216 – 300 sq ft | 108 – 150 sq ft |
| Flagstone (irregular) | 140 – 160 lbs | 13 – 14 | 78 – 84 sq ft | 39 – 42 sq ft |
| Riprap (2–6 in) | 100 – 120 lbs | 17 – 20 | 102 – 120 sq ft | 51 – 60 sq ft |
Coverage is approximate — actual results vary by stone shape, voids between pieces, and layer thickness. Order 10–15% extra for irregular terrain.
Frequently Asked Questions
At 2 inches deep with pea gravel (100 lb/ft³), you need about 0.83 tons. At 3 inches, you need about 1.25 tons. At 4 inches, about 1.67 tons. Multiply by your rock type's density divided by 100 for other materials.
2 inches for decorative ground cover, 3 inches for walkways and garden paths, 4 inches for driveways and high-traffic areas, and 6+ inches for drainage projects and dry creek beds.
Pea gravel is smooth and rounded (100 lb/ft³), great for paths and decorative use. Crushed stone is angular (110 lb/ft³), compacts better for driveways and base layers. Crushed stone locks together; pea gravel shifts underfoot.
Pea gravel $30-55/ton, crushed stone $30-50/ton, river rock $45-100/ton, decomposed granite $35-60/ton, lava rock $50-80/ton. Prices vary by region and supplier. Delivery typically adds $50-150 per order.
Yes, landscape fabric is strongly recommended. It prevents weeds from growing through, stops rock from sinking into soil, and makes future removal or replacement much easier. Overlap edges by 6-12 inches.
Add 10% for simple rectangular areas, 15% for irregular shapes, and 20% for complex projects like dry creek beds. This accounts for spillage, uneven ground, and settling. Better to have extra than run short.
Multiply cubic yards by the rock's density in lb/ft³, then divide by 2,000. For example, 1 cubic yard of pea gravel (100 lb/ft³) = 100 × 27 ÷ 2,000 = 1.35 tons.
Remove existing vegetation and debris. Level the area and compact the soil. Lay landscape fabric overlapping edges by 6-12 inches. Add edging to contain the rock. Then spread rock evenly to your desired depth.