Gravel Calculator
This gravel calculator works out how many tons and cubic yards of gravel you need for a base, driveway, path or patio. Enter the area and the depth, pick the material so the density is right, and it converts the volume into the tons your supplier actually sells by. Gravel is priced and delivered by weight, not volume, which is why the density matters.
How to use this calculator
- Enter the length and width of the area you are covering.
- Enter the compacted depth you want when the job is finished, not the loose depth you will spread.
- Pick the material, which sets the density used to convert cubic yards to tons.
- Order by the ton. Yards are useful for checking a quote, but almost every supplier bills by weight.
If the material you are buying is recycled concrete rather than quarried stone, use the crushed concrete calculator instead. The math is the same but the density differs, and that page explains why the 1.4 tons per yard figure most calculators use is the wrong one for a finished base.
How deep should the gravel be?
Depth is where most orders go wrong, and the answer depends on what is going on top.
| Application | Compacted depth |
|---|---|
| Base under a concrete slab | 4 in minimum |
| Base under pavers or a patio | 4 to 6 in |
| Walkway or garden path | 2 to 4 in |
| Residential gravel driveway | 6 to 8 in, often in two lifts |
| Driveway carrying heavy vehicles | 8 to 12 in |
For slab work, Concrete Network's guidance on subgrades and subbases puts the floor at 4 inches: the entire subbase and base system should be at least 4 inches thick, thicker if the engineer calls for it. It also describes what good base material looks like, a compactible granular fill with 10 to 30 percent fines and no clay, silt or organic material, and notes that crushed recycled concrete aggregate works well.
Compaction is the other half of it. Specifications commonly call for the soil to be compacted to 95 percent of maximum modified Proctor density, which in practice means running a plate compactor or roller over the material in lifts rather than dumping the full depth at once. Loose gravel settles, so if you spread exactly the calculated depth and then compact it, you will finish low. Spread proud and compact down to the target.
Gravel density: why tons and yards are not interchangeable
A cubic yard of gravel is a fixed volume. Its weight depends on the stone size, how angular it is, and how much fine material is mixed in. Inch Calculator gives the usual ranges: gravel from 1/4 inch to 2 inch at 2,800 to 3,400 lbs per cubic yard, which is 1.4 to 1.7 tons; pea gravel at 2,500 to 3,000 lbs, or 1.25 to 1.5 tons; and larger rock from 2 to 6 inch at 2,200 to 2,800 lbs, or 1.1 to 1.4 tons.
Two practical consequences. Larger stone weighs less per yard, because bigger voids mean more air in the same volume. And a well-graded crusher run with plenty of fines weighs more than clean single-size stone, because the fines fill those voids. That is also why crusher run compacts into a solid base and clean stone does not.
If your supplier quotes a density, use theirs rather than the default in the dropdown. Local stone varies more than any online table admits.
The formula
Find the volume in cubic yards, then multiply by the density in tons per cubic yard:
Tons = (Length ft × Width ft × Depth ft ÷ 27) × tons per cubic yard
Worked example. A 40 ft × 12 ft driveway at 6 inches deep: 40 × 12 × 0.5 = 240 cubic feet, or 8.9 cubic yards. At 1.5 tons per cubic yard for crusher run, that is about 13.3 tons. At a clean 1.25 tons per yard it would be 11.1 tons, which is why the material dropdown is not decoration.
After the base
If the gravel is going under a concrete slab specifically, gravel under a concrete slab is the page you want: it carries the code depth, which stone to use, and where the vapor retarder goes. Otherwise, gravel is usually step one. Once the base is in and compacted, size the concrete going on top with the concrete slab calculator, or the concrete driveway calculator for a drive. If you are pouring a ramp over compacted fill, the concrete ramp calculator handles the sloped geometry. Buying sand and stone to mix the concrete itself rather than to build a base? The concrete mix calculator converts a mix ratio into the sand and gravel volumes to order.
Frequently asked questions
How much gravel do I need?
Multiply length by width by depth in feet to get cubic feet, divide by 27 for cubic yards, then multiply by the density in tons per cubic yard. Most gravel runs 1.25 to 1.5 tons per cubic yard, so a 40 by 12 foot driveway at 6 inches deep needs roughly 13 tons.
How many tons of gravel are in a cubic yard?
Usually 1.25 to 1.7 tons, depending on the stone. Gravel from 1/4 to 2 inch runs 1.4 to 1.7 tons per cubic yard, pea gravel 1.25 to 1.5, and larger 2 to 6 inch rock 1.1 to 1.4, because bigger stone leaves bigger voids.
How deep should gravel be under a concrete slab?
At least 4 inches of compacted granular base, and thicker if an engineer specifies it. Use a compactible fill with some fines rather than clean single-size stone, since clean stone will not lock together.
How deep should gravel be for a driveway?
6 to 8 inches compacted for a residential driveway, usually placed in two lifts and compacted separately. Driveways taking delivery trucks or equipment want 8 to 12 inches.
Should I order gravel by the ton or the yard?
By the ton, because that is how nearly every supplier bills and how the truck is weighed. Cubic yards are useful for checking that a quote matches the volume you actually need.
Is gravel the same as crushed concrete?
They do the same job as a compactable base, but crushed concrete is recycled and usually cheaper, while gravel is quarried stone. Use the crushed concrete calculator if you are buying recycled material.