Calculate how much gravel you need from the area you want to cover and the depth you want to fill, or work backward from a known amount of gravel to find the depth it will cover or its cost.
Gravel Formula
The calculator first turns your area and depth into a volume in cubic feet, then converts that volume into cubic yards, weight, and cost using the density of the gravel you select.
V_ft3 = Area_ft2 * Depth_ft
Cubic_Yards = V_ft3 / 27
Tons = (V_ft3 / 27) * Density_lb_per_yd3 / 2000
When you solve for depth instead of volume, the calculator rearranges the first equation:
Depth_ft = V_ft3 / Area_ft2
Variables:
- V_ft3: volume of gravel in cubic feet.
- Area_ft2: the surface area you are covering, in square feet. For a rectangle this is length times width, for a circle it is pi times radius squared, and for a triangle it is one half base times height.
- Depth_ft: how deep the gravel layer is, in feet.
- Cubic_Yards: volume converted to cubic yards, since there are 27 cubic feet in a cubic yard.
- Density_lb_per_yd3: the weight of one cubic yard of the gravel type, in pounds.
- Tons: total weight in US tons, where one ton equals 2000 pounds.
The "Solve for" selector controls which of these the calculator returns. "How much gravel I need" takes your area and depth and reports volume, weight, bags, and cost. "How deep my available gravel will cover" takes a known amount of gravel and an area and returns the depth. "Cost of a known amount of gravel" skips the area entirely and prices out a volume or weight you already have. The gravel type sets the density used in the weight and tonnage lines, and the optional compaction and waste settings increase the order quantity so you do not come up short.
Gravel Types and Typical Densities
Density is the link between volume and weight. The values below are the approximate weights the calculator uses for each gravel type. Confirm the figure with your supplier, since moisture and stone shape change it.
| Gravel type | Pounds per cubic yard | Tons per cubic yard |
|---|---|---|
| Regular gravel | 2,835 | 1.42 |
| Pea gravel | 2,565 | 1.28 |
| Crushed stone #57 | 2,431 | 1.22 |
| Dense graded aggregate | 3,374 | 1.69 |
| Decomposed granite | 2,781 | 1.39 |
| Lava rock | 1,391 | 0.70 |
The next table shows depths that are common for different uses. Multiply the area by these depths to size a job quickly.
| Use | Typical depth |
|---|---|
| Walkway or garden path | 2 in |
| Ground cover or mulch layer | 2 to 3 in |
| Driveway top layer | 4 in |
| Full driveway over base | 6 to 8 in |
Example Problems
Example 1. You want to cover a rectangular patio that is 20 feet long and 12 feet wide with 3 inches of regular gravel. The area is 20 times 12, which is 240 square feet. A 3 inch depth is 0.25 feet, so the volume is 240 times 0.25, which is 60 cubic feet. Divided by 27 that is 2.22 cubic yards. Using a density of 2,835 pounds per cubic yard, the weight is 2.22 times 2,835, which is about 6,300 pounds, or 3.15 tons.
Example 2. You have 4 cubic yards of pea gravel and a 300 square foot area to cover. Four cubic yards is 4 times 27, which is 108 cubic feet. The depth it will cover is 108 divided by 300, which is 0.36 feet, or about 4.3 inches.
Frequently Asked Questions
How many tons of gravel are in a cubic yard?
It depends on the gravel type, but most gravel runs between 1.2 and 1.7 tons per cubic yard. Regular gravel is close to 1.4 tons per cubic yard, while a lighter material like pea gravel is closer to 1.3 tons and a heavy dense graded aggregate can reach 1.7 tons. The calculator uses the density for the type you pick so the tonnage matches the material.
Should I order extra gravel?
Yes. Gravel settles and compacts after it is spread, and some is always lost to spillage and uneven ground. Adding 5 to 10 percent to the calculated amount is common. The advanced options let you set a waste percentage and a compaction factor so the order quantity already includes that cushion.
What depth of gravel should I use?
For paths and ground cover, 2 to 3 inches is usually enough. For a driveway, plan on about 4 inches for a top layer, or 6 to 8 inches total if you are building up from a fresh base. Deeper layers hold up better under vehicle traffic but use more material.
