Rock Calculator

Calculate how much landscaping rock you need for rectangular, circular, or irregular areas. Get cubic yards, tons, and bags needed for riprap, river rock, decorative boulders, and more — plus an estimated material cost. Free, no signup required.

Landscaping Rock Volume Calculator

Rock Calculation Formulas by Shape

Rectangle: Area = Length × Width (sq ft) Circle: Area = π × Radius² (sq ft) Irregular: Enter measured area directly Volume (cu ft) = Area × (Depth / 12) Cubic Yards = Volume / 27 Tons = Cubic Yards × Density (tons/yd³) Bag count (0.5 cu ft bags) = Volume / 0.5

Rock Type Density Reference

Rock TypeDensity (tons/yd³)Best Uses
River Rock / Rounded1.35Decorative beds, water features, drainage
Crushed Stone / Riprap1.4Erosion control, drainage, driveways
Granite / Fieldstone1.5Heavy erosion control, retaining walls
Lava Rock0.9Decorative mulch alternative, fire pits
Marble Chips1.45Formal gardens, decorative pathways
Pea Gravel1.3Pathways, play areas, under decks

Frequently Asked Questions

What is the difference between riprap and river rock? +
Riprap refers to large, rough, angular rocks used primarily for erosion control along slopes, embankments, and waterways. River rock (also called rounded gravel) is naturally worn smooth by water and is used mainly for decorative purposes in gardens and landscaping. Riprap is heavier and more angular; river rock is rounder and more aesthetically appealing.
How many bags of rock do I need for a small area? +
For small projects, landscaping rock is often sold in 0.5 cubic foot bags. A 100 sq ft area at 2 inches deep needs about 16.7 cubic feet, which requires 34 bags. For areas larger than about 2 cubic yards (54 cubic feet), it is more economical to order bulk delivery by the cubic yard or ton.
Should I add extra for waste when ordering rock? +
Yes. Most landscaping professionals recommend adding 10–15% to your calculated amount to account for settling, uneven distribution, and waste. For irregular areas or sloped terrain, adding 15–20% is a better buffer to avoid running short.

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