Landscape Rock Calculator

Enter the length and width of your bed, choose a depth and a rock type, and get the volume in cubic feet and cubic yards, an estimated weight in tons, and how many bags you would need if you buy bagged stone.

How the landscape rock calculator works

Landscape rock is sold by volume (cubic yards, or cubic feet for bags) or by weight (tons). The calculator first finds the area of your bed, multiplies it by the depth to get volume, and then converts volume into weight using a typical bulk density for the stone you choose.

1. Area: length × width for a rectangle; π × (diameter ÷ 2)² for a circle; base × height ÷ 2 for a triangle.
2. Volume in cubic feet = area in square feet × depth in inches ÷ 12.
3. Cubic yards = cubic feet ÷ 27 (a cubic yard is 3 ft × 3 ft × 3 ft).
4. Tons = cubic yards × density in tons per cubic yard.
5. Bags = cubic feet ÷ bag size, rounded up to whole bags.

The optional extra percentage covers stone that settles into the soil or fabric, spills during spreading and uneven ground. Five percent is a reasonable default for a level bed; use ten percent for irregular shapes or a bed you will edge by eye.

How deep should landscape rock be?

Depth is the number that changes your order the most, so choose it for the job the rock has to do. As a rule, the layer should be at least twice as deep as the largest stones so the base is fully covered.

Deeper is not always better. Very thick gravel around plant stems holds heat and can make it hard to water; a thinner layer over good fabric usually looks cleaner and costs less.

Worked example

A bed 12 feet long and 4 feet wide has an area of 48 square feet. At a depth of 3 inches the volume is 48 × 3 ÷ 12 = 12 cubic feet, which is 12 ÷ 27 = 0.44 cubic yards. With river rock at about 1.35 tons per cubic yard, that is roughly 0.6 tons, or about 1,200 pounds. Adding 5% for settling gives 12.6 cubic feet — 26 bags of 0.5 cubic feet each. For a bed this size bagged stone is practical; for anything above about one cubic yard, bulk delivery is usually cheaper per ton.

Cubic yards, tons or bags: which should you order?

Landscape suppliers usually sell bulk stone by the cubic yard or by the ton, while garden centres sell bags of 0.5 or 0.75 cubic feet, sometimes marked by weight such as 40 or 50 pounds. One cubic yard is 27 cubic feet, so it equals 54 bags of 0.5 cubic feet. Bulk orders often have a minimum delivery and a delivery fee, so bags can be cheaper for small beds even though the stone costs more per yard.

• 1 cubic yard covers about 324 sq ft at 1 in deep, 162 sq ft at 2 in, 108 sq ft at 3 in and 81 sq ft at 4 in.
• A ton of typical gravel is roughly 0.7–0.75 cubic yards.
• A standard pickup bed holds roughly 1–2 cubic yards of rock by volume, but weight is the real limit — check your truck's payload before hauling stone yourself.

Rock density and why it matters

Density is the weight of a cubic yard of loose stone. Most dense landscape stones such as river rock, pea gravel, crushed granite and limestone fall between about 1.3 and 1.5 tons per cubic yard. Lava rock is porous and much lighter, often around half a ton per cubic yard, which is why a ton of lava rock covers far more ground. Wet stone weighs more than dry stone, and suppliers quote different figures for the same product, so if you order by weight, ask the yard for the density they use and type it into the custom field.

Preparing the area before the rock goes down

• Remove turf and weeds, and grade the soil so water drains away from buildings.
• Install edging — steel, aluminium, plastic or stone — to stop rock migrating into lawn.
• Lay a woven landscape fabric under decorative gravel to reduce weeds and keep stone from sinking; overlap seams by several inches.
• For paths, compact a base of crushed stone before the top layer so the surface stays firm.
• Spread rock with a rake held tines-up for the final level, then water lightly to wash off dust.