River rock calculator

Where river rock goes

River rock is smooth, water-rounded stone, usually larger than gravel. It is chosen for looks and for places water runs: dry creek beds, downspout outlets, swales and borders. Because the pieces are large, the layer has to be deep enough for stones to overlap and hide the ground or fabric underneath.

For a channel, measure the width across the top and use an average depth. For an irregular run, split it into sections.

Worked example: dry creek bed

Weight of river rock

We found no reliable published density specific to river rock, so the general dry-gravel value (105 lb/ft³) source is used, with the published gravel range source shown for context. Large rounded stones leave more space between them than finer material, and suppliers' river rock products vary widely in size, so the weight is approximate. If the supplier quotes “tons per yard” for the product, enter it.

Reading the result

Each line of the order sheet answers a different question. Read them in order: geometry first, then your allowances, then the quantity you can actually buy.

Calculated volume

Area × depth — pure geometry, before any allowance.

+ Compaction

Extra loose material if the depth is a compacted depth. Shown only when set.

+ Waste

Your margin for spillage, edges and uneven ground, applied after compaction.

Purchase volume

What to buy: volume × (1 + compaction) × (1 + waste). The exact figure.

Estimated weight

Purchase volume × the density shown. Only as accurate as that density.

Bulk order

Purchase volume and weight rounded up to the next ½ yd³ / ½ ton (½ m³ / ½ t in metric).

Bags / cost

Whole bags of the size you entered; cost = your price × the matching quantity.

What this calculator assumes

• Dimensions are the plan area that will actually be covered.
• Depth is an average across the area.
• Areas are flat; slopes aren't adjusted for.
• Density is a loose bulk density — a general published value unless you replace it.
• Waste and compaction are multiplied, not added.
• Bags are rounded up to whole bags; bulk orders up to the next ½ unit.
• Uses the general dry-gravel value. Large rounded stones leave more air between them, which changes weight per yard.

It can't see your site or your supplier's stone. What the calculators cannot know · Full methodology

Common mistakes with this calculator

1. Measuring to the top of the biggest stone

   What goes wrong: Overstates the depth and the order.

   How to avoid it: Use the average depth of the layer.

2. Assuming every gravel weighs the same

   What goes wrong: The published gravel range of 91–120 lb/ft³ turns 2 yd³ into anything from 2.46 to 3.24 tons.

   How to avoid it: Ask the supplier for their weight per yard or conversion factor and type it into Density.

3. Measuring a curved or L-shaped area as one rectangle

   What goes wrong: Using the longest length and widest width counts ground that isn't there and over-orders.

   How to avoid it: Split the area into rectangles, circles and triangles and add each one. See the measuring guide.