River Rock Calculator
Gravel & StoneMeasurements in, purchasing amount out
How the River Rock Calculator works
The calculator finds volume first, then applies the selected material’s estimated bulk-density range to show weight. Your suggested order adds 10% for settling, uneven ground, and small measurement errors.
Using your measurements
12 ft × 8 ft × (3 in ÷ 12) ÷ 27 = 0.89 cu yd
Density assumption: 1–3 in river rock (1½ in average) · 2,400–2,700 lb/yd³
The full breakdown
How much river rock your landscaping beds, dry creeks, or drainage projects need
The river rock calculator above converts length, width, and depth into cubic yards, tons, and bags as you type. It covers the common sizes — 3/4 in, 1½ in and 1–3 in, 2–4 in, and cobble — for decorative borders, French drains and swales, and bulk quarry orders; getting the quantity right up front avoids short-load fees and a stalled job.
River rock is naturally rounded stone, smoothed by water in riverbeds or by mechanical tumbling. Unlike angular crushed gravel, it does not interlock, which leaves open voids between the stones and makes it a favorite for low-maintenance beds, foundation splash strips, planters, and erosion-control dry creek beds. For angular decorative stone, lava rock, and decomposed granite, use the landscape rock calculator.
Converting square feet into weight matters because bulk suppliers and quarries sell river rock by the ton, while retail centers sell it in 0.5 cubic-foot (about 50 lb) bags. Standard 1–3 inch and 3/4–1 inch river rock weighs approximately 2,500 to 2,700 lb per cubic yard (1.25 to 1.35 tons/yd³). Larger 2–4 inch river rock and 4–8 inch cobble leave bigger gaps between stones, bringing bulk density down to roughly 2,200 to 2,600 lb per cubic yard.
Thickness is where most river rock projects fall short. Because individual stones are three-dimensional spheres and ovals, spreading a layer thinner than twice the stone’s diameter exposes the underlying landscape fabric. Our calculator includes a recommended 10% ordering buffer so your installation achieves 100% ground coverage with zero visible bare spots.
River rock sizes and stone varieties alter bulk density
Volume remains constant at 27 cubic feet per cubic yard, but tonnage shifts with stone size, mineral origin, and moisture content. Fine pebbles pack tightly with minimal air gaps, while oversized cobbles create large voids.
| River Rock | Weight |
|---|---|
| 3/4–1 in river rock | 2,500–2,700 lb/yd³ |
| 2–4 in river rock | 2,300–2,600 lb/yd³ |
| 4–8 in cobble | 2,200–2,500 lb/yd³ |
Recommended river rock depths by stone size and application
To ensure complete ground coverage and block sunlight from reaching weed seeds, always install river rock at a minimum depth equal to at least two full stone layers.
| 3/4–1 in river rock (garden borders & flower beds) | 2–3 in (5–7.5 cm) |
|---|---|
| 1½ in / 1–3 in river rock (general landscaping & paths) | 3–4 in (7.5–10 cm) |
| 2–4 in river rock (dry creek beds & gentle slopes) | 4–6 in (10–15 cm) |
| 4–8 in cobble / bull rock (erosion control & drainage swales) | 6–10 in (15–25 cm) |
| French drain trench & downspout rock basins | 8–16 in (20–40 cm) |
| House perimeter drip edge / foundation splash strip | 3–4 in (7.5–10 cm) |
Bagged vs. bulk river rock & pricing breakdown
Bagged river rock (0.5 cu ft or 50 lb bags at home centers) is convenient for small planter accents and touch-ups. When your project requires more than 1 cubic yard (about 54 bags of 50 lb), buying bulk river rock by the ton from a landscape supply yard saves 50% to 75% on material costs.
A standard pallet holds 49 to 56 bags of 50 lb river rock (approx. 2,450–2,800 lb / 1.2–1.4 tons).
Two critical river rock landscaping mistakes to avoid
Laying river rock too thin over landscape fabric
Spreading 2-to-3-inch river rock at a 1-inch depth leaves gaps where the dark weed fabric shows through and shifts under rain or foot traffic. Always calculate a depth at least 2 to 2.5 times the stone diameter for full opacity.
Using cheap perforated plastic instead of heavy non-woven geotextile
Smooth river rocks are heavy and slip on slick plastic sheeting, while plastic tears easily and traps standing water. Always install heavy-duty 4 oz to 6 oz non-woven geotextile landscape fabric pinned with steel staples to prevent weed growth and stone sinking.
River rock, specifically
River rock questions people actually ask
Why add 10% to the calculated amount?
Extra material covers small dips, settling, spillage, and measurements that are not perfectly square. The calculated amount remains visible so you can compare both figures.
Are bag counts based on the same amount?
Both are shown. “Calculated” bags cover the measured volume; “Order” bags include the 10% allowance and round partial bags up to whole bags.
How accurate is the weight estimate?
Volume comes directly from your dimensions. Weight is a range because moisture, particle size, composition, and compaction change bulk density.
What is river rock?
River rock is an aggregate of naturally rounded, smooth stones that have been smoothed over time by running water in rivers and streams, or mechanically tumbled. Common varieties include granite, basalt, quartz, and limestone pebbles in sizes ranging from 3/8 inch to over 8 inches.
How much river rock do I need?
Multiply the length by the width in feet to get square footage, multiply by depth in feet (depth in inches divided by 12), and divide by 27 to calculate cubic yards. Multiply cubic yards by 1.3 to estimate tons. For example, a 100 sq ft garden bed at 3 in depth requires 0.93 cubic yards (about 1.2 tons or 50 bags of 50 lb).
How much does river rock cost?
Bulk river rock typically costs $40 to $85 per ton ($55 to $110 per cubic yard) for standard mixed colors from a landscape supplier, plus delivery; premium stone such as Mexican beach pebbles or white quartz runs $120 to $250+ per ton. Bagged river rock costs $4 to $8 per 50 lb bag, or $160 to $320 per ton. DIY installed cost runs about $2 to $5 per square foot, and professional installation $4 to $9.
How much does a yard of river rock weigh?
One cubic yard of river rock weighs approximately 2,400 to 2,700 pounds (1.2 to 1.35 tons). Denser small gravel (3/4–1 in) weighs around 2,600 lb/yd³, while larger 2–4 in rock weighs closer to 2,400 lb/yd³ due to larger void spaces.
What does river rock look like?
River rock features smooth, rounded, oval or oblong pebbles with soft, water-worn edges. Colors range from earthy blends of tan, gray, brown, rust, and beige to striking solid black, charcoal, snow white, and variegated river stone.
How much does a ton of river rock cover?
One ton (2,000 lb) of river rock covers roughly 100 sq ft at 2 in depth, 65 sq ft at 3 in depth, or 45–50 sq ft at 4 in depth. Coverage decreases as stone size increases.
Is river rock good for drainage?
Yes, river rock is one of the best materials for drainage. Because the stones are smooth and round, they do not compact tightly together, leaving ample voids for high-volume water flow in French drains, dry creek beds, downspout basins, and swales.
Is river rock the same as gravel?
No. River rock is naturally smoothed and rounded by water action, creating a decorative, non-compacting stone. Standard landscape gravel and crushed stone are mechanically broken with sharp, angular edges designed to interlock and compact.
How long does river rock last?
River rock is practically permanent. Unlike wood mulch that decomposes and requires annual replacement, natural river stone never rots, fades, or blows away in heavy winds, lasting decades with minimal maintenance.
Should I put river rock around my house?
Yes, installing a 2-to-3-foot border of river rock around your foundation protects siding from splashback mud, prevents termite and rodent attraction (unlike wood mulch), improves roof drip-line drainage, and serves as an effective fire-resistant barrier.
What are the different types of river rock?
Common types include standard mixed river rock, Mexican beach pebbles (smooth black/charcoal), rainbow river stone, Delaware river rock, Colorado red river stone, white quartz river pebbles, and large river cobble (4–8 in bull rock). For crushed and decorative stone that is not water-worn, use the landscape rock calculator.
What size river rock is best for landscaping?
For garden beds and borders, 1–2 inch or 1–3 inch river rock is ideal because it stays in place when using a leaf blower and covers fabric well. For walkways, 3/8 to 3/4 inch is more comfortable to walk on, while 2–4 inch and larger cobbles excel in dry creeks and water features.
How thick should river rock be?
River rock should be spread at a thickness equal to at least 2 to 2.5 times the stone size. For 1-inch stones, spread 2 to 3 inches thick; for 2-to-3-inch stones, spread 4 to 5 inches thick.
How many bags of river rock in a cubic yard?
A cubic yard contains 27 cubic feet. Since standard retail bags hold 0.5 cubic feet (approx. 50 lb), it takes 54 bags of river rock to equal one cubic yard.
What should I put under river rock?
Always install commercial-grade, needle-punched non-woven geotextile fabric (4 oz or heavier) secured with 6-inch landscape staples. Do not use thin plastic sheeting or organic mulch under river stone.