Gravel Calculator

What this gravel calculator takes and returns

Give it a shape, the size of the area, the depth you want and the stone you are buying, and it returns cubic yards, tons, 50 pound bag counts and a cost estimate. The depth is the compacted depth, which is the number that matters once the stone is rolled.

That makes this the page for structural stone: driveway bases, parking pads, drainage beds, shed floors and patio sub-bases. Rounded decorative stone spread thin over fabric is a different job, with different math and different depths. The pea gravel calculator covers that side, including the half-cubic-foot bags sold at garden centers; this page assumes one material, one depth and a tonnage you will order from a quarry.

Two allowances sit inside the result. The first converts your compacted depth into the loose volume you have to buy, because stone shrinks as it is compacted. The second adds a waste percentage, which is the stone that ends up in the grass, in the wheelbarrow and in the low spot you did not see.

From square feet to tons in two steps

Step one, volume. Area in square feet times depth in inches, divided by 12 for feet, divided by 27 for cubic yards. A 288 square foot pad at 4 inches: 288 x 4 / 12 / 27 = 3.56 cubic yards of compacted stone.

Step two, weight. Multiply by the density of the stone in tons per cubic yard, minus nothing, because a ton is a ton. The trick is that your 3.56 cubic yards are compacted while the quarry sells loose stone, and loose stone takes up more room.

The conversion comes from the U.S. Army's earthmoving field manual, FM 5-434. Its material table gives sand or gravel a loose-to-compacted factor of 0.86, which means one cubic yard loose becomes 0.86 cubic yards compacted. Run backwards, 3.56 / 0.86 = 4.13 cubic yards of loose stone has to arrive to leave 3.56 cubic yards in place.

Then weight: 4.13 x 1.50 = 6.20 tons of crusher run for that layer. Skip the loose step and you under-order by about 16 percent, which on a driveway is a visible thin spot near the garage door.

Worked example: a 24 by 12 foot driveway

A two-car driveway 24 feet long and 12 feet wide is 288 square feet. It gets a 4 inch base of crusher run and a 2 inch top of #57 stone, both compacted. Crusher run is taken at 1.50 tons per loose cubic yard and clean #57 at 1.40, with 5 percent waste.

So the order is about 9.55 tons: roughly 6.2 tons of crusher run and 2.9 tons of clean stone, ordered as two loads. At $40 a ton that is 9.55 x 40 = 382.00 dollars of stone, before delivery.

The widget works one layer at a time, so run it once with crusher run at 4 inches and once with #57 at 2 inches, then add the two tonnages.

Bag the same job and the arithmetic changes character. One cubic yard is 27 cubic feet, so 6.20 loose cubic yards is 167.67 cubic feet, which is 335 bags at half a cubic foot each. At $4.50 a bag the same stone costs 335 x 4.50 = 1,507.50 dollars, and someone has to carry it.

How deep should each layer be?

Depth is where most estimates go wrong, and it is decided by traffic and soil, not by the size of the pile you have room for. Iowa State University Extension's farm driveway guide asks for a compacted base of at least 8 inches, built from about 8 to 12 inches of three-quarter to three inch crushed stone with around 4 inches of compacted fines on top.

Ohio's specifications put a hard ceiling on how thick one pass can be: the Item 411 stabilized crushed aggregate specification allows a maximum compacted lift of 6 inches, and most compactors do better work at 4. That is why a 10 inch base is built in two or three lifts rather than dumped and rolled once.

Soft ground is the expensive variable. A driveway over clay or old fill needs the thicker section, and often a layer of large stone at the bottom to bridge the weak spot. Ordering the thin version and adding stone later costs more than doing it once, because the second delivery is a second mobilization fee.

Tons, cubic yards and what the yard is selling

Quarries quote in tons because their scales weigh trucks, and homeowners think in cubic yards because that is what a wheelbarrow and a tape measure produce. The bridge between them is density, and density is a property of the stone, not a constant.

The first three rows are loose stone, which is what a dump truck delivers. The last row is the Ohio DOT's conversion factor for Item 411 crushed stone compacted in place, 3,800 pounds per cubic yard, and it shows why the same job weighs more after rolling.

Two cross-checks keep an estimate honest. A ton of #57 spread 2 inches deep covers about 116 square feet, so the 2.89 tons of top stone in this driveway covers 2.89 x 116 = 335 square feet, a little more than the 288 square feet the job needs, which is the waste allowance doing its job. And one cubic yard fills 27 cubic feet, about 13 wheelbarrows of 2 cubic feet each. If your number implies 40 wheelbarrows for a job you can see from the kitchen window, the depth or the units slipped.

Bags, bulk bags and a dump truck

Three ways to buy the same stone, three different price points. Bagged stone at a home center runs about 0.5 cubic feet per bag, so 54 bags make a cubic yard. Bulk bags, the woven cubes on a pallet, usually hold 1 cubic yard or a ton depending on the supplier. A dump truck delivers loose tons and tips them where you point.

Bagged stone is for touch-ups, small beds and the last half inch of a job. At 54 bags per cubic yard, a 5 cubic yard driveway is 270 bags, and that is a trailer, a weekend and a sore back. Bulk bags save the handling but cost more per ton than loose. Loose delivery wins on any job above about 3 cubic yards, as long as a truck can reach the spot.

Ask three questions before ordering: what does your stone weigh per cubic yard, is the price per ton or per cubic yard, and what is the smallest load you will deliver. A yard that sells by the cubic yard and converts at 1.4 tons will beat one that converts at 1.6 for the same pile, and the difference on 10 yards is a couple of tons of stone.

Mistakes that cost a second delivery

The waste percentage is the cheapest insurance on the page. Five percent covers normal spillage and an uneven subgrade. Ten percent is right when the area is irregular, the edges are soft, or the stone has to be carried any distance by hand.

Compacting too thick a lift is the second mistake. Stone that goes down 8 inches and gets one pass with a plate compactor looks finished and stays loose underneath, then ruts under a tire. Spread in 4 inch loose lifts, mist lightly, and compact each one before the next.

Do not skip the fabric on soft or weedy ground. Woven geotextile keeps subgrade soil from pumping up into the stone, which is what turns a clean base into a muddy one after a wet spring. Overlap the rolls 12 inches and keep the fabric tight.

Finally, measure the area twice. A driveway that is 12 feet wide at the garage and 10 feet at the street averages 11, and using 12 for the full length over-orders by about 9 percent. On a 9.55 ton order that is nearly a ton of stone sitting in a pile at the end of the job.

What the cost estimate leaves out

The widget multiplies tons by a price per ton, which is the number a quarry quotes at the scale. Delivery is usually separate: a short haul runs a flat fee, a longer one runs per mile, and small loads carry a minimum. Two loads of 5 tons can cost more in delivery than one load of 10 tons, which is an argument for getting the tonnage right the first time.

Spread the cost over the years and the picture changes. A 9.55 ton driveway at $40 a ton is $382.00 of stone, and with delivery and a rented plate compactor the project might land near $700. Over a ten year life that is about $70 a year, against patching a thin driveway every spring.

Prices vary by region, by quarry and by season, so treat the cost line as a planning figure and get a quote before you commit. The tonnage is the part of this page you can trust to the decimal; the dollars depend on who is selling.