What Is Road Base? Material, Uses and Weight per Yard

What is road base? Road base is a crushed rock blend that runs from stones about an inch or so across all the way down to sand-sized grit and dust. That full range of sizes is the whole point. When it is spread, dampened and compacted, the small pieces fill the gaps between the big ones and the layer locks into a hard, stable platform. It goes under asphalt, concrete and pavers, it builds gravel driveways and parking pads, and it is one of the most common bulk materials a quarry sells. The tricky part is that almost every region calls it something different, so this guide covers what it is made of, the names you will hear, how much it weighs, and how to work out an order.

Base tonnage calculator →

What road base is made of

Most road base is crushed limestone, granite, trap rock or another hard local stone, run through a crusher and screened so the finished pile has a planned mix of coarse stone, medium stone and fines. Engineers call this a dense-graded aggregate, because the particle sizes are spread out enough that very little open space is left once it is packed. The fines act like a binder. They will not glue the rock together the way cement does, but with the right amount of moisture and a good compactor they let the layer reach a tight, firm surface that resists rutting.

Some suppliers also sell recycled road base made from crushed concrete or crushed asphalt. It behaves much like the virgin stone version and is often a little cheaper. Ask whether it has been screened for rebar, wire, wood and trash, and see a sample pile before you take a full load. Our post on recycled concrete under asphalt covers where it works well.

What road base is called in different places

A lot of confusion about road base is really a naming problem. Ask for it by the local name and the person at the scale house will know exactly what you mean. A few names you may run into:

Aggregate base, Class 2 base, or ABC (aggregate base course) in much of the West and in many state specs.
Crusher run in the Southeast and Mid-Atlantic. See crusher run for driveways.
Dense grade aggregate (DGA) in parts of the Ohio Valley and Mid-Atlantic. Our DGA driveway guide goes deeper.
21A in Virginia, CA-6 in Illinois, Class 5 in Minnesota, and Item 4 in New York. Each has its own page here: 21A gravel, CA-6 gravel, Class 5 and Item 4.
Flex base in Texas, and plain base rock or road gravel in a lot of rural yards.

These products are close cousins, not exact twins. Each state or quarry writes its own size limits, so one yard’s base may be a little coarser or carry more fines than another’s. If you are building to a plan, ask for the spec sheet. For a home driveway or pad, any of them will do the job.

What road base is used for

Under asphalt. A compacted base spreads wheel loads so the thin asphalt layer on top does not crack. The driveway base calculator works out tons for this layer.
Under concrete slabs and footings. It gives the slab an even, well-drained bed. See gravel base under a concrete slab.
Under pavers. It is the standard base below the sand bedding layer. How deep paver base should be covers depths for walkways and driveways.
Gravel driveways and parking pads. Many rural drives are nothing but a thick layer of road base, sometimes topped with a cleaner stone.
Shed pads, shoulders and trench backfill where a firm, compactable fill is needed.

How much road base weighs

Road base sold by the ton has to be turned into volume before you can plan a job, and the answer changes with how tightly it is packed. These are typical planning ranges for crushed stone base; your stone, its moisture and the quarry’s gradation will move the numbers.

Condition	Approximate weight per cubic yard	Tons per cubic yard
Loose, in the truck or pile	about 2,500 to 3,000 lb	about 1.25 to 1.5
Spread and fully compacted	about 3,600 to 3,900 lb	about 1.8 to 1.95

The gap between those rows is the reason base orders often come up short. A yard of loose stone shrinks noticeably once it is rolled, so plan from the compacted thickness you want, not the loose depth you dump. For more on converting, see tons to cubic yards for gravel and gravel weight per yard.

How many tons of road base you need

A handy rule for compacted road base is about 12 pounds per square foot for every inch of finished depth, or roughly 0.006 tons per square foot per inch. Multiply your area by the compacted depth and by that factor, then add 5 to 10 percent for waste, low spots and edges.

Tons ≈ area (sq ft) × compacted depth (in) × 0.006
Coverage of one ton ≈ 167 ÷ compacted depth (in), in square feet

Compacted depth	Approx. area one ton covers	Tons per 100 sq ft
2 inches	about 80 sq ft	about 1.2
4 inches	about 40 sq ft	about 2.4
6 inches	about 28 sq ft	about 3.6
8 inches	about 21 sq ft	about 4.8

Example: a 12 by 40 foot driveway with 6 inches of compacted base. 12 × 40 = 480 square feet. 480 × 6 × 0.006 = about 17.3 tons. Add 10 percent and order about 19 tons. Our 4-inch base tonnage post has more worked sizes.

How deep to put it down

Depth depends on the soil and what will drive on it. Firm, well-drained ground under a walkway or patio may need only about 4 inches. Car driveways commonly get 6 to 8 inches, and soft clay, wet spots or regular truck traffic call for more, sometimes 10 to 12 inches with a separation fabric under it. When in doubt, the cheapest place to add strength is the base, not the asphalt or concrete on top.

Tips for placing and compacting road base

Prep the ground first. Strip sod and topsoil, cut out soft spots, and shape the subgrade to the slope you want the finished surface to have.
Work in lifts. Spread and compact in layers. With a walk-behind plate compactor, keep each lift to a few inches. Compacting gravel base in lifts explains why.
Get the moisture right. Road base packs best when it is damp but not soupy. A dusty pile will not lock up, and a saturated one pumps under the compactor. Squeeze a handful: it should hold shape without dripping.
Crown or slope it. Dense base sheds water rather than draining it, so build in a crown or a cross slope so water runs off instead of sitting on top.
Keep the edges tight. Run the compactor along the outer edge more than once and, for driveways, carry the base a little wider than the finished surface.

Road base vs clean stone

The opposite of road base is a washed, open-graded stone such as #57 stone. With the fines removed, it drains freely and works well in French drains and under some permeable paving, but it does not pack into a hard surface on its own and tends to roll underfoot. Road base is the better pick for strength and a firm driving surface; clean stone is the better pick where water has to pass through. Crushed stone vs gravel covers more of the differences.

Questions people ask

What is road base made of?

Crushed hard stone such as limestone, granite or trap rock, screened so it holds a mix of stone sizes from about an inch down to fine dust. Recycled road base uses crushed concrete or asphalt instead.

Is road base the same as crusher run?

Close enough for most home projects. Crusher run is the common Southeast name for a dense-graded base, and other regions call similar products ABC, DGA, Class 5, CA-6, 21A, Item 4 or flex base. Exact gradations differ by state and quarry.

How much does a ton of road base cover?

About 40 square feet at 4 inches of compacted depth, or about 28 square feet at 6 inches. Divide 167 by the compacted depth in inches for a quick estimate, then add 5 to 10 percent for waste.

Can road base be used as a driveway surface?

Yes. Many rural driveways are just compacted road base. It packs firm but can get dusty in dry weather and soft when soaked, so crown it to shed water and plan on adding a little each year or two.

Does road base drain well?

Not especially. The fines that let it pack tight also slow water down, so it sheds water instead of letting it through. Use a washed, open-graded stone where drainage is the goal.

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