Landscape Rock Calculator: Tons and Cubic Yards for Your Yard

Landscape rock is a durable, low-maintenance alternative to mulch that suppresses weeds, retains moisture, and adds visual interest to landscaping. Calculating how much you need — and whether to order in cubic yards or tons — can be confusing without a clear method. This guide simplifies the calculation for any type of decorative stone.

Recommended Depth by Stone Size

Coverage depth depends on the size of the rock:

• Pea gravel (3/8 inch): 2-3 inches deep
• Small decorative rock (1 inch): 2-3 inches deep
• Medium rock (1.5-2 inch): 3-4 inches deep
• Large river rock (3-5 inch): 4-6 inches deep
• Boulders: placed individually

Calculating Cubic Yards

The formula: cubic yards = (length in feet × width in feet × depth in inches) ÷ 324. For a 20×30-foot planting bed at 3 inches deep: (20 × 30 × 3) ÷ 324 = 1,800 ÷ 324 = 5.56 cubic yards. Round up to 6 cubic yards. Add 10% for settling and uneven coverage: order 6.5 cubic yards.

Converting Cubic Yards to Tons

Many stone suppliers sell rock by the ton. To convert cubic yards to tons, multiply by the weight per cubic yard. This varies by stone type:

• Pea gravel: ~1.5 tons per cubic yard
• River rock (small): ~1.35 tons per cubic yard
• Lava rock: ~0.5 tons per cubic yard (very light)
• Crushed limestone: ~1.5 tons per cubic yard
• Decomposed granite: ~1.4 tons per cubic yard

For our 5.56-cubic-yard pea gravel example: 5.56 × 1.5 = 8.3 tons. Order 9 tons.

Cost Estimates by Stone Type

Pea gravel: $35-$55 per cubic yard or $25-$45 per ton. River rock: $55-$100 per cubic yard. Lava rock: $75-$150 per cubic yard. Decomposed granite: $40-$70 per cubic yard. Delivery charges ($50-$150) apply for bulk orders under a minimum (usually 5-10 cubic yards).

Weed Barrier Under Rock

Always install a quality woven weed barrier fabric before placing rock. It dramatically reduces weed growth and prevents rocks from sinking into the soil over time. Calculate fabric area the same as your rock area, with an extra 10% for overlap at seams.

Calculate your landscape rock. Use the Landscape Rock Calculator on diycalculator.net to convert between cubic yards and tons for any rock type and bed size.