Rock Mulch Calculator
Calculate decorative rock, gravel, bark dust, and stone by weight (tons) and cubic yards. Works for pea gravel, river rock, lava rock, and all rock mulch types.
Reviewed by the Pro Mulch Calculator Editorial Team · Last updated: July 2, 2026
How do I calculate rock mulch in cubic yards? The rock mulch calculator formula is Length x Width x Depth in inches / 324 = Cubic Yards. A 20 x 10 ft bed at 3 inches deep equals 1.85 cubic yards. Multiply yards by weight per yard (2,500-3,000 lbs for most rock) and divide by 2,000 to get tons.
Rock Mulch Calculator
Rock, gravel, stone, and bark dust coverage
Typical: 2-3" for decorative rock; 3-4" for weed control
Rock vs Bark - Weight & Cost Comparison
Enter your area to compare the weight and estimated cost of rock mulch vs bark dust for the same coverage area.
Rock Types (River Rock / Lava / Pea Gravel / Crushed)
Rock mulch comes in five main types: river rock, lava rock, pea gravel, crushed stone, and decomposed granite. River rock is smooth and decorative. Lava rock is porous and lightest. Pea gravel is small (1/4 to 3/8 inch) and used for paths. Crushed stone is angular and used for drainage. The Mulch and Soil Council (MSC) classifies all five as inorganic mulch under its product standards.
| Rock Type | Best Use | Weight / Cu Yd | Depth | Cost / Ton |
|---|---|---|---|---|
| Pea Gravel | Pathways, playgrounds, drainage | ~2,800 lbs | 2-3" | $25-$55 |
| River Rock (small) | Beds, borders, water features | ~2,700 lbs | 2-3" | $50-$100 |
| River Rock (large) | Slopes, drainage, accent | ~2,650 lbs | 3-4" | $60-$130 |
| Crushed Limestone | Driveways, paths, base layers | ~2,900 lbs | 2-4" | $20-$45 |
| Lava Rock | Desert/xeriscape, accent beds | ~3,000 lbs | 2-3" | $75-$160 |
| Decomposed Granite | Pathways, xeriscape, driveways | ~2,700 lbs | 3-4" | $35-$65 |
| Pumice | Lightweight accent, succulent beds | ~1,800 lbs | 2-3" | $80-$150 |
Tons vs Cubic Yards
Rock mulch suppliers sell by both tons (weight) and cubic yards (volume). One ton of pea gravel equals 0.625 cubic yards. One ton of river rock equals 0.57 to 0.71 cubic yards. Suppliers use tons for delivery pricing because trucks have weight limits. Use cubic yards for volume planning. Convert with: Tons = Cubic Yards x Weight per Yard / 2000. The stone mulch calculator above outputs both numbers from one input.
Coverage at 2in / 3in Depth
One cubic yard of rock mulch covers 162 sq ft at 2 inches deep or 108 sq ft at 3 inches deep. Decorative pathways use 2 inches over landscape fabric. Ground cover beds use 3 inches for full weed suppression. Drainage installs need 4 to 6 inches. Coverage stays the same across rock types since volume drives area, not weight.
Weight per Yard by Rock Type
Rock weight per cubic yard varies by density. Lava rock is lightest at 1,200 to 1,800 lbs per yard due to porous structure. Pea gravel sits at 2,700 to 2,800 lbs per yard. River rock weighs 2,500 to 3,500 lbs per yard. Crushed stone weighs 2,400 to 2,900 lbs per yard. A half-ton pickup truck holds only 0.5 cubic yards of most rock safely. Always confirm payload rating before self-haul.
What does the stone mulch calculator output?
The stone mulch calculator outputs cubic yards, total tons, square footage covered, and number of 0.5 cubic foot bags. Enter length, width, depth, and rock type. The calculator applies the correct weight factor for river rock, lava rock, pea gravel, or crushed stone. Add 10 percent buffer for settling and edge spill.
How does rock landscaping cost compare to wood mulch?
Rock landscaping costs 5 to 10 times more upfront than wood mulch. A 500 sq ft rock install runs $2,000 to $5,000. The same wood install runs $400 to $600. Rock pays back in 5 years through zero replacement. Wood needs annual top-dressing at $0.50 per sq ft.
Rock vs Bark Mulch - Which Should You Choose?
| Factor | Rock Mulch | Bark / Wood Mulch |
|---|---|---|
| Lifespan | Permanent | 1-4 years |
| Long-term cost | Lower (no replacement) | Higher (annual top-dressing) |
| Installation weight | Very heavy (1-1.5 tons/yd) | Light (0.2-0.35 tons/yd) |
| Summer heat | Gets very hot in sun | Stays cooler |
| Soil health | No benefit | Improves soil as it decomposes |
| Weed suppression | Good (with fabric underneath) | Good at 3"+ depth |
| Removal if needed | Very difficult and expensive | Easy - decomposes in place |
| Best climate | Dry, hot (low-water landscapes) | All climates |
Front Yard Rock Mulch - Landscape Design Tips
Rock mulch for front yards works best with drought-tolerant plants (ornamental grasses, lavender, salvia, sedum) and modern or desert landscape styles. Install landscape fabric beneath rock mulch to prevent gravel from mixing into soil over time. Use edging to contain rock at bed boundaries. For high-visibility front yard applications, river rock (small) or decomposed granite offer the most polished appearance.
FAQ
The rock mulch calculator formula is Length x Width x Depth in inches / 324 = Cubic Yards. A 20 x 10 ft bed at 3 inches deep equals 1.85 cubic yards. Multiply yards by weight per yard (2,500-3,000 lbs for most rock) and divide by 2,000 to get tons.
Rock mulch combined with landscape fabric provides excellent long-term weed suppression. Without fabric, soil mixes into the rock within 2 years and weeds take over. Wood mulch at 3-4 inches gives comparable weed control without needing fabric.
Rock mulch weighs 2,400 to 3,000 pounds per cubic yard. Pea gravel sits at 2,800 lbs. River rock weighs 2,500-3,500 lbs. Lava rock is lightest at 1,200-1,800 lbs per yard. A half-ton pickup holds only 0.5 cubic yards of rock safely.
Rock mulch needs 2 inches over fabric for decorative coverage, 3 inches for full ground coverage, and 4-6 inches for foundation drainage. Pea gravel pathways need 3 inches for foot comfort. Deeper than 4 inches wastes material with no visual benefit.
Rock mulch installed costs $4 to $10 per square foot. Material runs $50 to $150 per cubic yard. Labor adds $1 to $3 per square foot. Fabric underlayment adds $0.50 per square foot. A 500 sq ft front yard rock install totals $2,000 to $5,000.
Rock mulch needs commercial-grade woven landscape fabric underneath. Without it, soil mixes into the rock within 2 years and weeds take over. The National Association of Landscape Professionals (NALP) lists fabric as mandatory under any decorative rock installation.
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