ABC Gravel: Aggregate Base Course Size, Weight and Tons

ABC gravel is short for aggregate base course, the crushed stone with fines that goes down under driveways, parking pads, slabs and roads in North Carolina and in several other states that use the same name. It runs from about 1½ inches down to dust. Because it carries every size in between, it packs into a hard, stable layer when it is wetted and compacted, and that is exactly what you want under asphalt or concrete. For planning, figure about 1.8 tons of ABC for each cubic yard of finished, compacted base. This guide explains what the name covers, how ABC compares with crush and run and clean stone, how deep to lay it, and how to work out the tons.

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What ABC means

The term comes from the North Carolina Department of Transportation. Its standard specifications list a gradation called ABC, for Aggregate Base Course, and quarries across the state sell stone made to that blend. Homeowners pick up the abbreviation from the scale house and the delivery ticket, so you will hear “ABC stone,” “ABC gravel,” “ABC base” and sometimes “ABC rock” for the same product. Arizona suppliers also sell a material called ABC, but it is built to that region’s own specs, so do not assume an Arizona ABC and a North Carolina ABC are identical.

NCDOT’s coarse aggregate table sets the share of ABC, by weight, that must pass each sieve. In round terms it looks like this. Check the current NCDOT specification or the quarry’s test report if a permit or plan calls for certified material.

Sieve opening	Share passing (by weight)
1½ inch	100%
1 inch	75 to 97%
½ inch	55 to 80%
No. 4 (about 3/16 inch)	35 to 55%
No. 10	25 to 45%
No. 40	14 to 30%
No. 200 (dust)	4 to 12%

Read the bottom rows and you can see why ABC packs so well: a real share of the stone is sand-sized and finer, and it fills the gaps between the larger pieces. The spec also limits how plastic, or clay-like, that fine portion can be, so the base does not turn to mush when it gets wet. NCDOT lists a second blend, ABC(M), with looser limits for maintenance work such as stabilizing unpaved shoulders. If a yard offers both, the plain ABC is the one to use under pavement.

ABC vs crush and run, #57 and other base stone

Product	What it is	Fines?	Best use
ABC	Dense-graded crushed stone, about 1½ inches down to dust, made to a DOT base spec	Yes	Base under asphalt, concrete and pavers; gravel driveway base
Crush and run	A general name for crushed stone mixed with its own dust	Yes, amount varies	The same jobs as ABC; some yards use the two names for one product
#57 stone	Clean stone, about 1 inch to 1/2 inch, no dust	No	Drainage, French drains, under concrete where water must pass
#67 stone	Clean stone, about 3/4 inch down to 3/16 inch	No	Top dressing, drainage, pipe bedding

In many parts of North Carolina, a yard that sells “crush and run” is selling its ABC, so the names get used interchangeably. Elsewhere, crush and run can be looser in its makeup, which is why it pays to ask whether the product meets the DOT base spec. Our crusher run driveway guide covers that broader family. Other states sell the same kind of stone under their own names: 2A modified in Pennsylvania, 21A in Virginia, 304 in Ohio, CA6 in Illinois and Item 4 in New York. Georgia and South Carolina generally call it graded aggregate base, or GAB.

Where ABC works well

Under an asphalt driveway. Its main job. Laid in compacted layers over firm soil, ABC spreads wheel loads so the asphalt above does not rut or crack early. See why the base should be wider than the asphalt before you set the forms.
Under concrete slabs and pavers. Patios, walks, shed floors and garage slabs all benefit from a firm, even base that will not settle in spots.
Gravel driveways and parking areas. ABC makes a drivable surface on its own and is a common choice for rural drives and turnarounds.
Shed and equipment pads. A compacted pad of ABC a few inches above the surrounding grade keeps a shed or trailer level and off wet ground.

Where ABC falls short

Because the fines hold water and slow drainage, ABC is the wrong pick for French drains, behind retaining walls or anywhere water needs to move through the stone. Use a clean stone there. As a top surface on a driveway, ABC tends to lose its fines over time to rain and tires, which leaves loose stone on top, dust in dry spells and ruts on slopes. Plenty of owners accept that and add a few tons every few years. Others use ABC as the base and finish with a thin layer of cleaner stone, or pave over it.

How much ABC gravel weighs

Loose ABC, as it comes off the truck, commonly weighs around 1.4 to 1.5 tons per cubic yard. Compaction squeezes it down, so a cubic yard of finished base takes more stone, often about 1.8 tons. The exact number depends on the rock (much North Carolina ABC is crushed granite, but some is limestone or other rock), the moisture content and how hard it is rolled. When your supplier gives a figure, use theirs. Our gravel weight per yard chart lists other materials.

How deep to lay ABC

There is no single right depth, because it depends on the soil and what will drive on it. As a starting point for a home project:

Walks and patios: about 4 inches compacted.
Car driveways on firm, well-drained soil: about 6 inches compacted.
Soft clay, wet spots or heavy trucks: 8 inches or more, often over a separation fabric.

If a contractor, engineer or local permit sets a depth, follow it. Red clay that turns slick when wet is common in the Piedmont, and it is where a geotextile fabric under the stone does the most good.

How many tons of ABC you need

Measure the area in square feet and choose the compacted depth in inches. Then use:

Tons ≈ area (sq ft) × compacted depth (in) × 0.0055
Area one ton covers ≈ 180 ÷ compacted depth (in), in square feet

The 0.0055 factor assumes about 1.8 tons per compacted cubic yard, so it already accounts for the extra stone that compaction takes. Add 5 to 10 percent for uneven ground, curved edges or soft spots.

Compacted depth	Approx. area one ton covers	Tons per 100 sq ft
4 inches	about 45 sq ft	about 2.2
6 inches	about 30 sq ft	about 3.3
8 inches	about 23 sq ft	about 4.4

Example: a 10 by 50 foot driveway, 6 inches compacted. 10 × 50 = 500 square feet. 500 × 6 × 0.0055 = about 16.5 tons. With a little extra for the edges, order 17 to 18 tons. Truck sizes vary by hauler, and our guide to tons of gravel in a dump truck explains what each kind usually carries.

Example: a 12 by 16 foot shed pad, 4 inches compacted. 12 × 16 = 192 square feet. 192 × 4 × 0.0055 = about 4.2 tons. Order around 4½ tons.

Laying and compacting an ABC base

Remove sod, topsoil and soft material until you reach firm ground. Grade the soil so water will run off the finished surface.
Roll out fabric on clay or wet soil so the stone stays separate from the mud.
Spread the ABC in lifts of roughly 3 to 4 inches. A plate compactor cannot reach the bottom of a much thicker layer.
Dampen the stone and compact each lift until it stops moving under your boots. Water helps the fines lock in. Compacting a gravel base in lifts goes step by step.
Finish with a crown or steady slope so rain sheds off instead of soaking into the base.

Buying tips

Ask for it by name. Say “ABC” or “aggregate base course,” and if the yard calls it crush and run, ask whether it is made to the DOT base spec.
Ask what rock it is. Granite, limestone and recycled concrete versions can differ in color, weight and dust.
Price it delivered. The trip from the quarry often costs more than the stone. A yard close to your job may beat a cheaper price per ton farther away.
Plan the drop spot. A loaded dump truck is heavy. Have it dump where you need the stone, and keep it off septic fields, soft lawn and thin pavement.

Questions people ask

What is ABC gravel?

ABC stands for aggregate base course. It is a dense-graded crushed stone, about 1 1/2 inches down to dust, made to a state DOT base specification. The name is most common in North Carolina. It compacts into a firm base for driveways, slabs and roads.

Is ABC the same as crush and run?

Often, in North Carolina. Many yards there use the two names for the same base stone. Elsewhere, crush and run can be a looser mix of stone and dust, so ask whether it meets the DOT base spec if that matters for your job.

How much does a ton of ABC gravel cover?

At about 1.8 tons per compacted cubic yard, one ton covers roughly 45 square feet at 4 inches compacted, 30 square feet at 6 inches, or 23 square feet at 8 inches.

How much does a yard of ABC weigh?

Loose ABC commonly weighs around 1.4 to 1.5 tons per cubic yard. Compacted in place, a cubic yard of base often takes about 1.8 tons. Rock type and moisture change the figure, so use your supplier's number when you have it.

Can ABC gravel be used as a driveway surface?

Yes. It packs into a drivable surface and is common on rural driveways. Over time rain and traffic wash out the fines on top, so expect some loose stone, dust and ruts on slopes, and plan to add stone every few years.

Is ABC or #57 stone better under a driveway?

For the base, ABC is usually the better choice because its fines let it compact hard. #57 is clean stone that drains well but does not lock together, so it suits drainage layers and French drains more than a load-bearing base.

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