What Is the Gravel Calculator?
The Gravel Calculator estimates how much loose aggregate is needed to cover an area to a given depth. It gives the result as a volume in cubic yards and cubic feet, and as a weight in tons and pounds, because suppliers sell by either measure depending on the region and the material.
It is useful for driveways, garden paths, drainage trenches, patio bases, shed foundations and the compacted layer under concrete slabs. The same calculation applies to crushed stone, pea gravel, river rock, road base and sand. Only the density changes.
How the Calculator Works
The tool multiplies the length and width of the area to get square feet, then multiplies by the depth converted to feet. That gives cubic feet. Dividing by 27 gives cubic yards.
To convert volume to weight, it multiplies the cubic yards by the density of the material. Typical gravel and crushed stone weigh about 1.4 tons per cubic yard. Dense graded road base is heavier, and rounded stones such as pea gravel are lighter because they pack with more air between them.
The calculator adds a percentage for compaction and spillage. Angular crushed stone can compact by 10 to 15 percent under a plate compactor, so the loose volume you order must be greater than the finished volume.
The Gravel Formula
Volume (cubic feet) = Length × Width × Depth (in) ÷ 12
Cubic yards = Cubic feet ÷ 27
Tons = Cubic yards × Density (tons per cubic yard)
Typical densities
- Gravel and crushed stone: 1.4 tons per cubic yard
- Dense road base: 1.5
- Sand: 1.35
- River rock: 1.3
- Pea gravel: 1.25
These are averages for dry material. Wet stone weighs more.
Step-by-Step Explanation
- Measure the length and width of the area in feet.
- Decide the depth of the layer in inches and divide by 12.
- Multiply length, width and depth in feet to get cubic feet.
- Add 10 percent for compaction and spillage.
- Divide by 27 to get cubic yards.
- Multiply by the material’s density to get tons.
Worked Example
A gravel parking pad is 20 feet long and 10 feet wide, with a 3 inch layer of crushed stone.
- Area: 20 × 10 = 200 square feet.
- Depth in feet: 3 ÷ 12 = 0.25.
- Volume: 200 × 0.25 = 50 cubic feet.
- With 10 percent extra: 55 cubic feet.
- Cubic yards: 55 ÷ 27 = 2.04.
- Tons: 2.04 × 1.4 = 2.85.
You would order 3 tons. A standard pickup can carry about half a ton to one ton safely, so delivery is the practical option here.
How to Use the Calculator
- Enter the length and width of the area.
- Enter the depth of the gravel layer.
- Set the extra percentage. Use 10 percent or more for material that will be compacted.
- Choose the material so the right density is applied.
- Press Calculate.
- Read tons and cubic yards and order whichever unit your supplier uses.
For areas that are not rectangular, find the square footage first with the Square Footage Calculator. When gravel is a base for another surface, the next step is the Paver Calculator for a patio or the Concrete Calculator for a slab. For general fill, topsoil and mulch where weight does not matter, the Cubic Yard Calculator is simpler. Post holes for fencing often get a few inches of drainage gravel, which the Fence Calculator helps you plan around.
Practical Tips
- Ask the supplier for the density of the specific product. A local quarry will know the figure for its own stone.
- Order in one delivery. Delivery charges are usually per trip, and a second small load costs more than a slightly larger first one.
- Lay landscape fabric under decorative gravel to slow weeds and stop stone sinking into the soil.
- Install edging before spreading. It keeps gravel in place and makes the depth consistent.
- Compact base layers in lifts of no more than 3 to 4 inches. Thick layers do not compact fully.
- For driveways, build in layers: large stone at the bottom, smaller graded stone above, and fine gravel on top.
- Have the truck spread the load along the driveway while dumping if the driver is able to. It saves hours of raking.
Common Mistakes
Ordering by volume when the supplier sells by weight. Know both figures before you call.
Ignoring compaction. Crushed stone settles noticeably when compacted. A 4 inch finished layer needs about 4.5 inches of loose material.
Laying decorative stone too deep. Pea gravel deeper than about 2.5 inches is hard to walk on because feet sink into it.
Too thin a driveway base. A single 2 inch layer over soil disappears into the ground within a season.
Using rounded stone as a structural base. Round stones do not lock together. Bases need angular crushed stone with fines.
Forgetting drainage slope. A gravel surface should fall about 2 percent away from buildings.
Recommended Depths
- Decorative beds and paths: 2 to 3 inches.
- Patio and paver base: 4 to 6 inches of compacted crushed stone.
- Driveways for cars: 8 to 12 inches in total, in two or three layers.
- French drains: fill the trench around the pipe, usually 12 inches or more.
- Under concrete slabs: 4 inches of compacted stone.
Choosing a Gravel Type
Crushed stone with fines, often sold as crusher run or road base, compacts into a firm surface and is the usual choice for bases and driveways. Clean crushed stone without fines drains freely and is used around foundations and in drains. Pea gravel and river rock are rounded and comfortable underfoot, which suits paths and play areas, but they shift and need edging. Decomposed granite packs into a firm, natural-looking path.
Bags or Bulk?
Bagged gravel is sold in half cubic foot bags. One cubic yard is 54 of them. Bags make sense for a few square feet of top-up. For anything over about half a cubic yard, bulk delivery is far cheaper per ton and saves a great deal of lifting.
Preparing the Ground
Good gravel work starts below the gravel. Strip grass and topsoil down to firm subsoil, because organic material decomposes and settles. Shape the subgrade so water drains away, compact it, and lay geotextile fabric on soft or clay soils to keep the stone from mixing with the soil over time. On a slope, cross drains or a crowned centre keep runoff from washing fine material away. Spending an hour on the subgrade usually saves a re-top a year later.
Maintaining a Gravel Surface
Gravel moves under tyres and rain. Rake displaced stone back into wheel tracks a few times a year, fill potholes with fresh material and compact them, and plan to top up a driveway with a thin layer every two to three years. Use this calculator with a depth of 1 inch to estimate a top-up load.
Estimating Cost
Gravel is priced per ton or per cubic yard, with a separate delivery charge that depends on distance and load size. To estimate the cost, multiply the tons from this calculator by the price per ton and add delivery. Ask whether there is a minimum load and whether a larger truck would be cheaper than two trips. Decorative stone such as river rock or coloured granite can cost several times as much as plain crushed stone, so many people use an inexpensive compacted base for most of the depth and a thin layer of the decorative stone on top. For a 3 inch path, 2 inches of base and 1 inch of decorative gravel gives the same appearance for considerably less money.