Cubic Yard Calculator for Rock

A cubic yard calculator for rock tells you how many cubic yards of crushed stone, gravel, or boulders you need to order based on the length, width, and depth of the area you want to fill. You enter the three dimensions in feet (or inches), and the calculator returns the volume in cubic yards, plus the approximate weight in tons for a typical rock density. This is the number you give to a landscape supplier so you don’t overpay for extra material or run short in the middle of a project.

Formula

The volume of rock is simply the volume of a rectangular prism: length × width × depth. Because rock is sold by the cubic yard, you convert cubic feet to cubic yards by dividing by 27 (since 1 yard = 3 feet, and 3 × 3 × 3 = 27). The formula is:

V (yd³) = (L × W × D) / 27

• L = length of the area, in feet
• W = width of the area, in feet
• D = depth of the rock layer, in feet (convert inches to feet by dividing by 12)
• V = volume in cubic yards

For weight, multiply the volume in cubic feet by the rock density in pounds per cubic foot, then divide by 2,000 to get tons. A typical density for crushed stone is about 100 lb/ft³ (1,600 kg/m³), but it varies from about 90 lb/ft³ for loose gravel to 130 lb/ft³ for some dense basalt.

Worked Example

Using the default values from the calculator: length = 10 ft, width = 5 ft, depth = 4 in, density = 100 lb/ft³.

1. Convert depth to feet: 4 in ÷ 12 = 0.333 ft
2. Calculate volume in cubic feet: 10 × 5 × 0.333 = 16.65 ft³
3. Convert to cubic yards: 16.65 ÷ 27 = 0.617 yd³
4. Calculate weight: 16.65 ft³ × 100 lb/ft³ = 1,665 lb
5. Convert to tons: 1,665 ÷ 2,000 = 0.83 tons

The calculator rounds the cubic yards to 0.62 and the tons to 0.83. So for a 10×5 foot area at 4 inches deep, you would order about 0.62 cubic yards, or roughly 0.83 tons of rock.

Why Use Cubic Yards Instead of Tons or Bags?

Rock is sold in three ways: by the cubic yard (bulk delivery), by the ton (weighed at the quarry), and by the bag (at home centers). A cubic yard is a volume measure, which is what you need to cover an area. Tons are a weight measure, which is how trucks are loaded. The two are connected by density, but if you only know the area and depth, you must calculate volume first. Bags are convenient for small projects but are wildly inefficient for anything larger than a few square feet—one 0.5-cubic-foot bag covers only 1.5 square feet at 4 inches deep, so a 10×5 area would need about 11 bags, which costs far more per yard than bulk.

How to Measure Your Project Area

Accurate measurements are the difference between a smooth project and a trip back to the supplier. Follow these steps:

• Use a tape measure or measuring wheel for straight runs. For circular areas, measure the radius (half the diameter) and use Ï€ × r² for area.
• For irregular shapes, break them into rectangles and triangles, calculate each, and add them together.
• Measure depth based on the final compacted layer. If you are filling a hole, measure from the bottom to the desired finished level.
• If you are laying rock over landscape fabric, account for the fact that the rock will settle. Add 10–15% to your final volume to compensate for compaction and uneven ground.

Always measure in feet for length and width, and in inches for depth, since that matches the calculator inputs. If you measure in meters, convert to feet first (1 m = 3.28084 ft) or use a metric calculator.

Choosing the Right Rock Type and Depth

The depth you need depends on the rock size and its purpose. For decorative gravel that will be walked on, 2–3 inches is common. For a driveway that supports vehicles, you need 4–6 inches of crushed stone, often with a base layer of larger rock. For drainage or French drains, 6–12 inches may be required. The calculator lets you adjust depth, but the density also matters—lighter rocks like lava rock weigh less per cubic yard (about 70–80 lb/ft³), while heavier rocks like granite or basalt can exceed 120 lb/ft³. When ordering, tell the supplier the rock type and whether you need it delivered loose or in bulk bags. They will quote you in tons or yards, and you can use the calculator’s weight output to compare.

Common Mistakes and How to Avoid Them

• Mixing units: Entering depth in inches but length in feet without converting will give a volume 12 times too large. Always convert depth to feet or use the calculator’s built-in conversion.
• Forgetting to divide by 27: Cubic feet and cubic yards are different units. A cubic yard is 27 cubic feet, not 3.
• Ordering too little: Rock compacts and settles. A 10% overage is standard practice, especially for driveways or paths.
• Ignoring density: Ordering by tons without knowing the density can leave you short. For example, 1 cubic yard of pea gravel (about 95 lb/ft³) weighs about 1.28 tons, while 1 cubic yard of decomposed granite (about 110 lb/ft³) weighs about 1.49 tons.
• Rounding too early: If you round the cubic yards to 0.6 and then convert to tons, you get a slightly different answer than if you keep the full precision. Use the calculator’s output as-is, then round up when ordering.

Cost and Ordering Considerations

While the calculator gives you volume and weight, it cannot give a price because rock prices vary widely by region, type, and delivery distance. As a general rule, bulk rock is cheaper per yard than bagged rock, but delivery fees can add $50–$150 depending on distance and quantity. Many suppliers have a minimum order (often 1–2 cubic yards). To estimate cost, call a local quarry or landscape supply and ask for a per-ton or per-yard price for the specific rock you want. Then multiply by your calculated amount. Always ask if the price includes delivery and whether there is a surcharge for small orders. For large projects, consider ordering a full truckload (typically 10–20 tons) to reduce per-ton cost.

Safety and Handling Tips

Rock is heavy and can cause injury if handled improperly. When spreading rock by hand, use a wheelbarrow and a shovel, and wear gloves and sturdy boots. Avoid lifting rocks larger than 50 pounds—use a pry bar or machinery for boulders. If you are having rock delivered, keep children and pets indoors during dumping. For driveways, use crushed stone with angular edges (like #57 or #3) because it locks together better than smooth river rock. If you are laying rock over a slope, use a geotextile fabric to prevent it from washing away. Always spread rock evenly with a rake, and compact it with a plate compactor for driveways to avoid shifting.

Frequently Asked Questions

How many cubic yards do I need for a 10×10 area at 3 inches deep?

Using the formula: 10 × 10 × (3/12) = 25 cubic feet, divided by 27 = 0.93 cubic yards. So you would need about 1 cubic yard. At a density of 100 lb/ft³, that weighs about 1.25 tons.

How much does a cubic yard of rock weigh?

It depends on the rock type. Most crushed stone weighs between 2,400 and 2,900 pounds per cubic yard (about 1.2 to 1.45 tons). Lava rock is lighter at around 1,800–2,000 pounds per yard, while dense granite can be 2,800–3,200 pounds. Always confirm with your supplier.

Should I order in tons or cubic yards?

Order in the unit the supplier uses. Most quarries sell by the ton because they weigh trucks, but some sell by the cubic yard. Use the calculator to get both numbers, and ask the supplier which they prefer. If you order by ton, make sure the density you used matches the actual rock—ask the supplier for their density if unsure.

How much area does 1 cubic yard cover?

At 3 inches deep, 1 cubic yard covers about 108 square feet (since 1 yd³ = 27 ft³, and 27 / 0.25 = 108). At 4 inches deep, it covers 81 square feet. At 6 inches deep, it covers 54 square feet. The calculator can find the depth you need for a given area.

Can I use this calculator for river rock or pea gravel?

Yes, but adjust the density. River rock and pea gravel have a density of about 90–100 lb/ft³, while crushed stone is often 100–110 lb/ft³. The volume calculation is the same; only the weight changes. If you are ordering by the ton, use the correct density to avoid a shortfall.

Why is the calculator result different from what the supplier quoted?

Suppliers often add a compaction factor or round up to the nearest half-yard. They may also use a different density for weight. Your calculated volume is a good starting point, but always confirm the order amount with the supplier, and consider adding 10% for waste and settling.

Related

• Board Foot to Linear Foot Calculator
• Board Foot to Square Foot Calculator
• Board Foot Calculator: How to Measure Lumber

in l | Length | ft | 10 | 0
in w | Width | ft | 5 | 0
in d | Depth | in | 4 | 0
in density | Rock density | lb/ft³ | 100 | 0
out yards | Cubic yards | yd³ | (l * w * (d / 12)) / 27 | 2
out tons | Approx. weight | tons | ((l * w * (d / 12)) * density) / 2000 | 2