Landscape Rock Quantity Calculator: Math, Materials, and Buying Tips

Detailed math for estimating rock mulch quantities for perimeter beds and circular islands, plus buying strategies.

Rectangular Area Math

Area = Length × Width. Example: 300 sq ft ÷ 70 = ~3 cubic yards at 3" depth. (Note: 108 sq ft/CY is theoretical; 70 accounts for compaction/settling.)

Circular Island Math

Area = π × radius² (not 2πr). Example: 20' diameter = 10' radius. 3.14 × 100 = 314 sq ft. At 3" = ~3-4 CY.

Online Calculators

• GotMulch Calculator
• Wheel measure tool (~$20) invaluable for measuring beds

Buying Strategy

• Avoid bags: Expensive, hard to convert (9 bags × 3 CF = 1 CY)
• Buy by cubic yard from landscape yards
• If sold by ton: 1 CY dry rock ≈ 1.125 tons (2,250 lbs). Lose ~13% coverage vs. volume buying
• Small loads: 1 ton ≈ 1 CY for residential

Essential: Weed Fabric

Polypropylene fabric under rock (NOT black plastic—kills trees). Slows weeds, aids removal.

Metric Conversion

1 CY = 0.7646 cubic meters.