Calculate stone from your area dimensions, depth, and material density, or work backward to find how far a known weight of stone will go.
Stone Formula
When you solve for the stone needed, the calculator finds the volume of the space you are filling, then converts that volume to weight using the material density.
Volume = Area * Depth
Weight = Volume * Density
When you solve for coverage instead, the calculator starts from a known weight and target depth and returns the area that weight will cover.
Area = Weight / (Density * Depth)
- Area: the surface you are filling, found from length and width, diameter, or a base and height depending on the shape you pick.
- Depth: how thick the stone layer is, converted to the same length unit as the area.
- Volume: area multiplied by depth, reported in cubic yards, cubic feet, or cubic meters.
- Density: the weight of the material per unit of volume, chosen from the stone type or entered directly.
- Weight: the result for a project estimate, or your input when you are solving for coverage.
The shape selector controls how the area is computed: a rectangle uses length times width, a circle uses pi times the radius squared, and a triangle uses one half times base times height. The stone material selector sets the density for you, and choosing custom density lets you enter a supplier figure. The extra material option adds a percentage on top of the result to account for settling and waste, and the price field multiplies the final amount by your unit cost.
Stone Density and Coverage Reference
Use these values to sanity check a result or to pick a density when you do not have a supplier figure. Most clean crushed aggregates fall near 1.5 tons per cubic yard.
| Stone material | Approx. density (tons/yd³) |
|---|---|
| Crushed stone #57 | 1.20 to 1.35 |
| Crushed stone #411 / river rock | 1.40 to 1.55 |
| Pea gravel / marble chips | 1.25 to 1.40 |
| Dense graded aggregate | 1.65 to 1.85 |
| Decomposed granite | 1.35 to 1.55 |
| Lava rock | 0.65 to 0.80 |
| Riprap / coarse rock | 1.30 to 1.50 |
One cubic yard of stone covers this much area depending on how thick you spread it.
| Depth | Coverage per cubic yard |
|---|---|
| 1 inch | 324 sq ft |
| 2 inches | 162 sq ft |
| 3 inches | 108 sq ft |
| 4 inches | 81 sq ft |
Example Problems
Example 1. You are covering a rectangular bed 20 feet long and 12 feet wide with 3 inches of crushed stone #57. The area is 20 times 12, or 240 square feet. The depth of 3 inches is 0.25 feet, so the volume is 240 times 0.25, which is 60 cubic feet, or 2.22 cubic yards. At a density of 1.3 tons per cubic yard, that is about 2.89 tons. Adding 10 percent for settling gives roughly 3.18 tons.
Example 2. You have 5 tons of pea gravel at 1.3 tons per cubic yard and want to know the coverage at 2 inches deep. The volume is 5 divided by 1.3, or 3.85 cubic yards. At 2 inches deep each cubic yard covers 162 square feet, so 3.85 times 162 is about 623 square feet.
FAQ
How much extra stone should you order? Add 10 to 15 percent on top of the calculated amount. Stone settles and compacts after it is placed, and some is lost to spillage and uneven ground, so the extra keeps you from running short partway through the job.
Why does the calculator ask for a depth in inches when the area is in feet? The calculator converts every measurement to a common unit before multiplying, so the depth unit does not have to match the area unit. Spreading stone at 2 to 3 inches is typical for decorative ground cover, while 4 inches or more is common for driveways and high traffic areas.
Should you use tons or cubic yards when ordering? Suppliers sell stone both ways. Cubic yards measure volume and do not change with material, while tons measure weight and depend on density. If you order by weight, confirm the density the supplier uses, since a heavier stone yields fewer cubic yards per ton.
