Gravel calculator.

The single most common gravel ordering mistake is computing the raw volume of the hole and calling it the order quantity. A 12 by 40 foot driveway at 4 inches of finished thickness holds 5.93 cubic yards. Order 5.93 cubic yards of crushed stone and the finished surface will land near 3.2 inches after the roller passes, because dense-graded aggregate shrinks about 15 percent under proper compaction. FHWA earthwork guidance calls this out explicitly in the section on shrink-swell factors. Add transport settling and edge loss and the working number for a compacted base climbs to 20 percent over the target volume. That is not padding. It is the reason 4 inches of driveway stays 4 inches of driveway.

Decorative fill does not compact, so the overage shrinks to 10 percent and only covers what gets knocked off the edge by foot traffic or a rake pass. Pea gravel in a landscape bed at 2 inches does not need 20 percent; it needs 10 percent and nothing more.

The practical rule is to set the waste toggle on this calculator before touching anything else. Base course gets 20 percent. Decorative gets 10 percent. Anything else is a guess, and guesses are how the third truck shows up an hour after the contractor left.

Gravel driveways are one of the few residential construction decisions where cheaping out on thickness is both tempting and expensive. A 3 inch driveway looks fine the day it is finished. Six months in, the wheel tracks will be bare dirt and the crown will be gone. The reason is that dense-graded crushed stone spreads vehicle load through an inverted cone. Thin sections cannot spread far enough, so the tires drive the stone into the subgrade instead of over it. Port Aggregates and Penn State Extension both land on the same number: 4 inches of compacted base for light residential traffic, 6 inches for any truck or trailer that is going to park or turn.

Walkways tolerate less. A 3 inch walkway with a 2 inch compacted base reads well underfoot and holds up to seasonal freeze-thaw without gophering. Patios under pavers want a dense-graded base like crusher run or #57 at 4 inches compacted; the decorative layer on top is really bedding sand, not gravel, but the calculation for the base is identical to any other compacted course.

French drains are a different geometry entirely. The working volume is a trench, not a pad. A standard residential French drain runs 12 inches wide and 18 inches deep with a perforated pipe in the middle, surrounded by washed #57 stone and wrapped in filter fabric. The volume math is the same length times width times depth formula; the twist is that the depth is vertical, not horizontal, and the fabric has to wrap all the way around so the fines in the surrounding soil do not migrate into the drain and choke it. That failure mode is why unwrapped French drains quit working after a few years and why every DIY gravel guide that skips the fabric is selling you the next drainage job.

Gravel is not one thing. It is five or six things with different physics and different prices, and picking the wrong one is the fastest way to waste an afternoon.

Crushed stone is the workhorse. 3/4 inch dense-graded crushed limestone or granite, sometimes sold as crusher run or DGA (dense-graded aggregate). The angular particles lock together under compaction, which is what makes it the right choice for anything under load. Use it for driveways, base courses under pavers or slabs, and any compacted pad. It costs 35 to 90 dollars per cubic yard delivered depending on region, with the low end in limestone country and the high end wherever stone has to travel.

#57 stone is washed 3/4 inch to #4 aggregate. The washing and the open grading give it a high void ratio, which means water flows through it freely. That is exactly what a french drain wants and exactly what a driveway base does not want, because a high void ratio also means poor interlock under load. Use #57 for french drains, wet drainage swales, and as a drainage layer under slabs. Do not use it as a finished driveway surface unless you want the top layer to roll out of the wheel tracks every spring.

Pea gravel is 3/8 inch rounded stone, usually tan or multicolor, and it is purely decorative or recreational. The rounded shape is the whole point: rounded stones are gentle on bare feet and animal paws, which is why pea gravel shows up in play areas, dog runs, and ornamental beds. The same rounded shape is why pea gravel does not compact. It rolls. Put pea gravel on a driveway and it will end up in the street. Put it on a walkway over a compacted base and it holds just fine as long as the base is doing the structural work.

River rock is pea gravel's bigger cousin, 1 to 3 inches and purely decorative. It is the most expensive option on the list and for good reason: it is mechanically sorted, mostly washed, and priced for landscaping rather than construction. Use it where you want the look of a dry streambed or a drainage swale that doubles as a garden feature. Do not use it under anything that needs to bear load.

Decomposed granite, usually abbreviated DG, is a fines-heavy crushed product from granitic parent rock. Wet DG packs tight enough to behave like a paved surface under foot traffic, which is why it shows up on garden paths, patio floors, and xeriscape yards. It is denser per cubic yard than any of the other options because the fines fill the voids, so the tonnage math will come out higher for the same volume. GraniteCrete and other stabilized-DG suppliers publish density sheets that split hairs on moisture content; for ordering purposes the 1.40 tons per cubic yard midpoint used by this calculator is close enough.

Bulk gravel is dramatically cheaper than bagged gravel by the cubic foot, but bulk has a floor. Most landscape suppliers set a 1 ton delivery minimum, which is about 0.75 cubic yards. Below that, the delivery fee eats the per-yard savings. Dump-truck economics kick in around 3 to 5 tons, which is where free or discounted haul starts to show up within a 10 mile radius of the quarry. Above 10 tons, the per-ton price drops hard because the truck gets filled regardless.

The practical break-even is roughly 10 cubic feet of material. Under that, bagged from the home center is cheaper than delivered bulk after the fee. Over that, bulk wins, and bulk wins more the larger the job. The share output from this calculator includes both the yardage total and the 50 or 60 pound bag count so a user can make the call at the register.

One practical note: bagged gravel sold at Home Depot and Lowes is usually Quikrete or Sakrete all-purpose gravel, which is 3/8 inch washed crushed stone. It is closer to pea gravel than to crusher run. For a driveway base or a compacted pad, order bulk crusher run from a quarry, not bags from the home center. The product is different, and the compaction performance is different.

The gravel calculation is the easy part. The base under the gravel is where jobs actually succeed or fail, and the calculator cannot fix a bad subgrade.

For a driveway, start by stripping topsoil and any organic material down to firm subgrade. Organic matter decomposes, and decomposing material under a driveway is where the wheel tracks come from in year two. Once the subgrade is exposed, roll it with a compactor rental before any stone goes down. Proof-roll it by driving a loaded pickup across it; if the tires leave ruts, the subgrade needs geotextile fabric or additional compaction before gravel goes on top.

Woven geotextile between subgrade and base is the single cheapest upgrade a gravel driveway can get. A roll runs 50 to 150 dollars and covers a typical two-car driveway. It stops the base stone from mixing with the subsoil, which is the mechanism by which driveways sink over time. FHWA guidance is explicit that separation fabric dramatically extends service life on weak subgrades.

Edge restraint matters for walkways and patios more than for driveways. Without a buried timber, metal edge, or concrete curb, decorative gravel migrates sideways every time someone walks on it. Driveways are self-edging because the tires push material back toward the crown, but a pea gravel walkway without an edge will be a pea gravel front yard within two seasons.

Finally, crown a driveway. One to two percent slope from centerline to shoulder sheds water before it can pool and saturate the base. A flat driveway is a wet driveway, and a wet driveway is a rutted driveway. None of this shows up in the calculator, but every piece of it shows up in whether the finished job lasts five years or fifteen.