River Rock Calculator

River rock for beds, dry creek beds and drainage: cubic yards or m³, tons or tonnes, and bags for any mix of rectangles, circles and triangles.

River rock is smooth, rounded stone, from pebbles to several inches across, used for dry creek beds, borders, drainage swales and low-maintenance beds. Because the stones are larger than gravel, the layer needs to be deeper to cover the ground: a common rule of thumb is about twice the size of the stones. Enter the area and depth and this calculator gives the volume in cubic yards or m³, the weight in tons or tonnes, and the bags or bulk bags to buy. River rock is a little lighter per yard than crushed stone, as round stones leave bigger gaps, so it starts at 1.5 tonnes per m³ (about 1.26 tons per cubic yard).

Units
Bag sizes
Area
ft
ft
in
Feet and inches work too: type 12'6 or 12.5.
t/yd³
%
Volume
1.17 yd³

31.5 ft³ · 0.892 m³

Weight
1.47 tons

2,940 lb · 1.33 tonnes

Bags
63

0.5 ft³ bag

Bags needed by size
0.5 ft³ bag63
25 kg bag54
20 kg bag67
850 kg bulk bag2
How it was worked out
  1. Area: 12 ft × 10 ft = 120 ft²; × 3 in (0.25 ft) deep = 30 ft³
  2. 30 ft³ ÷ 27 = 1.11 yd³
  3. Plus 5% extra = 1.17 yd³
  4. 1.17 yd³ × 1.26 tons per yd³ = 1.47 tons (2,940 lb)
  5. 31.5 ft³ ÷ 0.5 ft³ per bag = 63, rounded up to 63 bags
Typical weights of common materials
Materialt/m³tons/yd³lb/ft³
Concrete2.402.02150
Gravel1.601.35100
Pea gravel1.601.35100
Crushed stone / crushed rock1.601.35100
River rock1.501.2694
Landscape rock / pebbles1.501.2694
Crushed limestone1.601.35100
Decomposed granite1.501.2694
Crusher run1.601.35100
Road base1.701.43106
Crusher dust1.501.2694
Aggregate (20 mm)1.601.35100
All-in ballast1.651.39103
MOT Type 1 sub-base1.801.52112
Sand1.601.35100
Topsoil1.301.1081
Garden soil1.301.1081
Fill dirt1.401.1887
Mulch0.350.2922
Bark chippings0.300.2519
Asphalt (compacted)2.321.96145

Loose, as-delivered figures; asphalt and concrete are as laid. Moisture, stone size and source change the real weight, so use your supplier's figure when you have it. Tons are US short tons (2,000 lb).

Common use cases

  • A dry creek bed or drainage swale
  • Low-maintenance beds and borders
  • Edging around a house to keep rain splash off walls
  • Covering the area around a downspout or soakaway

How to use

  1. Choose feet and inches or metres and millimetres, and the country whose bag sizes you want.
  2. Enter the length and width of the area, or switch the shape to a circle, triangle or a known area. Use Add another area for L-shapes and separate beds.
  3. Enter the depth of river rock. Lay it about twice as deep as the stones are wide: 2 to 3 inches for small rock, 4 to 6 inches for larger stones.
  4. Check the density and the extra allowance. Change the density if your supplier quotes a different figure.
  5. Read the volume, weight and bag count, and add a price per ton, cubic yard, m³ or bag for a cost estimate.

FAQ

How deep should river rock be?

A common rule of thumb is twice the size of the stones, so 2 to 3 inches (50 to 75 mm) for 3/4 to 1 1/2 inch rock, and more for larger stones. Put landscape fabric underneath to keep weeds down and the rock from sinking into the soil.

How much does river rock weigh?

Roughly 1.25 to 1.4 US tons per cubic yard (1.5 to 1.65 tonnes per m³) loose. It varies with the stone size and type, so check with your supplier.

How do I estimate a winding creek bed?

Break it into a few rectangles at its average width and add them as separate areas. For a natural look, creek beds are often lined with larger stones and filled with smaller ones; work out each layer separately.

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