Quick answer
Calculate area × installed depth for volume. Convert cubic feet to yards and multiply by the selected material density only when a weight estimate is needed. Rock size and density vary, so use supplier data.
Step by step
- Measure the bed Split curved or irregular beds into simple sections.
- Choose depth Use a depth suitable for the intended decorative or drainage use.
- Calculate volume Convert inches to feet before multiplying.
- Check weight Use the supplier's bulk density, not a generic rock weight.
Formula or rule of thumb
Example
A 150 ft² bed at 2 in deep is 25 ft³, or about 0.93 yd³.
Common mistakes
Using the same density for every stone, forgetting landscape fabric or edging needs, and confusing coverage depth with rock diameter.
Planning note: product yields, installation methods, site conditions and local requirements can change the final quantity. Use the exact manufacturer or supplier information before purchasing.
FAQ
Does larger rock cover differently?
Yes. Voids and placement affect actual coverage.
Can river rock be used for drainage?
Use project-specific drainage design; decorative coverage calculations are not drainage engineering.
Should I order extra?
Supplier and site conditions determine the allowance.