Does rock size affect how much I need?

Yes — larger rocks have more air gaps between them, so they weigh less per cubic yard than smaller rock, even though the volume calculation is the same. Adjust the density field for your rock size.

How deep should I lay river rock?

2-3 inches for pathways and borders, 3-4 inches for decorative beds, and 4-6 inches or more for drainage areas and dry creek beds.

What's the difference between river rock and pea gravel?

River rock is larger (typically 1-8 inches) with more shape and color variation, better for decorative landscaping and drainage. Pea gravel is smaller (1/4-3/4 inch) and more uniform, better for walkways and areas you'll walk on.

Should I use landscape fabric under river rock?

Yes, typically — fabric helps suppress weeds underneath the rock. Water can still drain through most landscape fabric while blocking weed growth.

River Rock Calculator

Calculate how much river rock you need for a decorative bed, dry creek bed, or drainage area, in cubic yards and estimated weight.

Length (ft)Width (ft)Depth (in)Density (example, editable by rock size) (lbs/yd³)~2600 for small 1-2" rock, ~2500 medium, ~2400 large

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This is the volume of river rock needed, with an estimated weight using your chosen density. Smaller river rock (1-2") packs more tightly and typically weighs more per cubic yard than larger rock (4-8"), which has more air gaps.

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How to Measure for River Rock

River rock is sold by volume for decorative beds, dry creek beds, and drainage areas. Measure the length and width of the area, and decide on a depth — typically 2-3 inches for pathways and borders, 3-4 inches for decorative beds, and 4-6+ inches for drainage areas.

How to Calculate River Rock Volume

Volume (cubic feet) = Length × Width × Depth, all in feet, divided by 27 for cubic yards.

River Rock Calculator Formula

Depth in feet = Depth in inches ÷ 12
Volume (cu ft) = Length × Width × Depth (ft)
Volume (cu yd) = Volume (cu ft) ÷ 27
Weight (tons) = Volume (cu yd) × Density ÷ 2,000 — density varies by rock size (see below)

How Much River Rock Do I Need?

It depends on your area, depth, and rock size. A small 12 ft × 8 ft bed at 3 inches deep needs under 1 cubic yard; a larger dry creek bed running the length of a yard can need several cubic yards.

River Rock Coverage Chart

Rock Size	Approx. Density	Coverage per Ton at 3" Depth
Small (1-2 in)	~2,600 lbs/yd³	~90 sq ft
Medium (2-4 in)	~2,500 lbs/yd³	~95 sq ft
Large (4-8 in)	~2,400 lbs/yd³	~100 sq ft

Smaller rock packs more tightly and weighs more per cubic yard; larger rock has more air gaps between stones and weighs less.

River Rock Measurement Examples

Small decorative bed: 12 ft × 8 ft, 3 inches deep, medium rock. Volume = 12 × 8 × 0.25 = 24 cu ft ÷ 27 ≈ 0.89 cubic yards ≈ 1.11 tons at 2,500 lbs/yd³.

Common River Rock Measurement Mistakes

Using one universal density figure regardless of rock size — always adjust for small, medium, or large rock. Not accounting for landscape fabric and edging separately (these are ordered independently, not part of the volume calculation). Underestimating depth for drainage applications, where 4-6+ inches is typically needed versus the 2-3 inches used for purely decorative borders.

How to Use This Calculator

Enter the length and width of the area, and your desired depth. Adjust the density based on your rock size — smaller rock packs denser than larger rock.

Formula & Methodology

Volume (cubic yards) = Length × Width × Depth (in feet) ÷ 27. Weight = Volume × Density.

Example: 10 ft × 10 ft bed, 2 in deep, small (1-2") river rock

10 × 10 × (2÷12) = 16.7 cubic feet ÷ 27 ≈ 0.62 cubic yards. At 2,600 lbs/yd³: about 0.8 tons.

River rock density varies meaningfully by stone size — commonly cited ranges are about 2,600 lbs/yd³ for small (1-2") rock, 2,500 for medium (2-4"), and 2,400 for large (4-8") rock, due to increasing air gaps between larger stones. These are commonly cited example figures, not a verified constant for your specific supplier's product — adjust the density field to match your supplier's actual figure if provided. Larger rock (over 3") is often estimated by a different coverage-per-ton rule rather than pure volume, since a single layer of large stone doesn't pack the same way — for large decorative boulders, confirm coverage directly with your supplier.

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Frequently Asked Questions

How much river rock do I need?: Multiply length by width by depth (all in feet), divide by 27 for cubic yards. A 10×10 ft bed at 2 inches deep needs about 0.62 cubic yards.
Does rock size affect how much I need?: Yes — larger rocks have more air gaps between them, so they weigh less per cubic yard than smaller rock, even though the volume calculation is the same. Adjust the density field for your rock size.
How deep should I lay river rock?: 2-3 inches for pathways and borders, 3-4 inches for decorative beds, and 4-6 inches or more for drainage areas and dry creek beds.
What's the difference between river rock and pea gravel?: River rock is larger (typically 1-8 inches) with more shape and color variation, better for decorative landscaping and drainage. Pea gravel is smaller (1/4-3/4 inch) and more uniform, better for walkways and areas you'll walk on.
Should I use landscape fabric under river rock?: Yes, typically — fabric helps suppress weeds underneath the rock. Water can still drain through most landscape fabric while blocking weed growth.

Last updated 7/14/2026